two version of R2R are here HEAD master

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diff --git a/.venv/lib/python3.12/site-packages/grpc/__init__.py b/.venv/lib/python3.12/site-packages/grpc/__init__.py
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+# Copyright 2015-2016 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""gRPC's Python API."""
+
+import abc
+import contextlib
+import enum
+import logging
+import sys
+
+from grpc import _compression
+from grpc._cython import cygrpc as _cygrpc
+from grpc._runtime_protos import protos
+from grpc._runtime_protos import protos_and_services
+from grpc._runtime_protos import services
+
+logging.getLogger(__name__).addHandler(logging.NullHandler())
+
+try:
+    # pylint: disable=ungrouped-imports
+    from grpc._grpcio_metadata import __version__
+except ImportError:
+    __version__ = "dev0"
+
+############################## Future Interface  ###############################
+
+
+class FutureTimeoutError(Exception):
+    """Indicates that a method call on a Future timed out."""
+
+
+class FutureCancelledError(Exception):
+    """Indicates that the computation underlying a Future was cancelled."""
+
+
+class Future(abc.ABC):
+    """A representation of a computation in another control flow.
+
+    Computations represented by a Future may be yet to be begun,
+    may be ongoing, or may have already completed.
+    """
+
+    @abc.abstractmethod
+    def cancel(self):
+        """Attempts to cancel the computation.
+
+        This method does not block.
+
+        Returns:
+            bool:
+            Returns True if the computation was canceled.
+
+            Returns False under all other circumstances, for example:
+
+            1. computation has begun and could not be canceled.
+            2. computation has finished
+            3. computation is scheduled for execution and it is impossible
+                to determine its state without blocking.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def cancelled(self):
+        """Describes whether the computation was cancelled.
+
+        This method does not block.
+
+        Returns:
+            bool:
+            Returns True if the computation was cancelled before its result became
+            available.
+
+            Returns False under all other circumstances, for example:
+
+            1. computation was not cancelled.
+            2. computation's result is available.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def running(self):
+        """Describes whether the computation is taking place.
+
+        This method does not block.
+
+        Returns:
+            Returns True if the computation is scheduled for execution or
+            currently executing.
+
+            Returns False if the computation already executed or was cancelled.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def done(self):
+        """Describes whether the computation has taken place.
+
+        This method does not block.
+
+        Returns:
+            bool:
+            Returns True if the computation already executed or was cancelled.
+            Returns False if the computation is scheduled for execution or
+            currently executing.
+            This is exactly opposite of the running() method's result.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def result(self, timeout=None):
+        """Returns the result of the computation or raises its exception.
+
+        This method may return immediately or may block.
+
+        Args:
+          timeout: The length of time in seconds to wait for the computation to
+            finish or be cancelled. If None, the call will block until the
+            computations's termination.
+
+        Returns:
+          The return value of the computation.
+
+        Raises:
+          FutureTimeoutError: If a timeout value is passed and the computation
+            does not terminate within the allotted time.
+          FutureCancelledError: If the computation was cancelled.
+          Exception: If the computation raised an exception, this call will
+            raise the same exception.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def exception(self, timeout=None):
+        """Return the exception raised by the computation.
+
+        This method may return immediately or may block.
+
+        Args:
+          timeout: The length of time in seconds to wait for the computation to
+            terminate or be cancelled. If None, the call will block until the
+            computations's termination.
+
+        Returns:
+            The exception raised by the computation, or None if the computation
+            did not raise an exception.
+
+        Raises:
+          FutureTimeoutError: If a timeout value is passed and the computation
+            does not terminate within the allotted time.
+          FutureCancelledError: If the computation was cancelled.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def traceback(self, timeout=None):
+        """Access the traceback of the exception raised by the computation.
+
+        This method may return immediately or may block.
+
+        Args:
+          timeout: The length of time in seconds to wait for the computation
+            to terminate or be cancelled. If None, the call will block until
+            the computation's termination.
+
+        Returns:
+            The traceback of the exception raised by the computation, or None
+            if the computation did not raise an exception.
+
+        Raises:
+          FutureTimeoutError: If a timeout value is passed and the computation
+            does not terminate within the allotted time.
+          FutureCancelledError: If the computation was cancelled.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def add_done_callback(self, fn):
+        """Adds a function to be called at completion of the computation.
+
+        The callback will be passed this Future object describing the outcome
+        of the computation.  Callbacks will be invoked after the future is
+        terminated, whether successfully or not.
+
+        If the computation has already completed, the callback will be called
+        immediately.
+
+        Exceptions raised in the callback will be logged at ERROR level, but
+        will not terminate any threads of execution.
+
+        Args:
+          fn: A callable taking this Future object as its single parameter.
+        """
+        raise NotImplementedError()
+
+
+################################  gRPC Enums  ##################################
+
+
+@enum.unique
+class ChannelConnectivity(enum.Enum):
+    """Mirrors grpc_connectivity_state in the gRPC Core.
+
+    Attributes:
+      IDLE: The channel is idle.
+      CONNECTING: The channel is connecting.
+      READY: The channel is ready to conduct RPCs.
+      TRANSIENT_FAILURE: The channel has seen a failure from which it expects
+        to recover.
+      SHUTDOWN: The channel has seen a failure from which it cannot recover.
+    """
+
+    IDLE = (_cygrpc.ConnectivityState.idle, "idle")
+    CONNECTING = (_cygrpc.ConnectivityState.connecting, "connecting")
+    READY = (_cygrpc.ConnectivityState.ready, "ready")
+    TRANSIENT_FAILURE = (
+        _cygrpc.ConnectivityState.transient_failure,
+        "transient failure",
+    )
+    SHUTDOWN = (_cygrpc.ConnectivityState.shutdown, "shutdown")
+
+
+@enum.unique
+class StatusCode(enum.Enum):
+    """Mirrors grpc_status_code in the gRPC Core.
+
+    Attributes:
+      OK: Not an error; returned on success
+      CANCELLED: The operation was cancelled (typically by the caller).
+      UNKNOWN: Unknown error.
+      INVALID_ARGUMENT: Client specified an invalid argument.
+      DEADLINE_EXCEEDED: Deadline expired before operation could complete.
+      NOT_FOUND: Some requested entity (e.g., file or directory) was not found.
+      ALREADY_EXISTS: Some entity that we attempted to create (e.g., file or directory)
+        already exists.
+      PERMISSION_DENIED: The caller does not have permission to execute the specified
+        operation.
+      UNAUTHENTICATED: The request does not have valid authentication credentials for the
+        operation.
+      RESOURCE_EXHAUSTED: Some resource has been exhausted, perhaps a per-user quota, or
+        perhaps the entire file system is out of space.
+      FAILED_PRECONDITION: Operation was rejected because the system is not in a state
+        required for the operation's execution.
+      ABORTED: The operation was aborted, typically due to a concurrency issue
+        like sequencer check failures, transaction aborts, etc.
+      UNIMPLEMENTED: Operation is not implemented or not supported/enabled in this service.
+      INTERNAL: Internal errors.  Means some invariants expected by underlying
+        system has been broken.
+      UNAVAILABLE: The service is currently unavailable.
+      DATA_LOSS: Unrecoverable data loss or corruption.
+    """
+
+    OK = (_cygrpc.StatusCode.ok, "ok")
+    CANCELLED = (_cygrpc.StatusCode.cancelled, "cancelled")
+    UNKNOWN = (_cygrpc.StatusCode.unknown, "unknown")
+    INVALID_ARGUMENT = (_cygrpc.StatusCode.invalid_argument, "invalid argument")
+    DEADLINE_EXCEEDED = (
+        _cygrpc.StatusCode.deadline_exceeded,
+        "deadline exceeded",
+    )
+    NOT_FOUND = (_cygrpc.StatusCode.not_found, "not found")
+    ALREADY_EXISTS = (_cygrpc.StatusCode.already_exists, "already exists")
+    PERMISSION_DENIED = (
+        _cygrpc.StatusCode.permission_denied,
+        "permission denied",
+    )
+    RESOURCE_EXHAUSTED = (
+        _cygrpc.StatusCode.resource_exhausted,
+        "resource exhausted",
+    )
+    FAILED_PRECONDITION = (
+        _cygrpc.StatusCode.failed_precondition,
+        "failed precondition",
+    )
+    ABORTED = (_cygrpc.StatusCode.aborted, "aborted")
+    OUT_OF_RANGE = (_cygrpc.StatusCode.out_of_range, "out of range")
+    UNIMPLEMENTED = (_cygrpc.StatusCode.unimplemented, "unimplemented")
+    INTERNAL = (_cygrpc.StatusCode.internal, "internal")
+    UNAVAILABLE = (_cygrpc.StatusCode.unavailable, "unavailable")
+    DATA_LOSS = (_cygrpc.StatusCode.data_loss, "data loss")
+    UNAUTHENTICATED = (_cygrpc.StatusCode.unauthenticated, "unauthenticated")
+
+
+#############################  gRPC Status  ################################
+
+
+class Status(abc.ABC):
+    """Describes the status of an RPC.
+
+    This is an EXPERIMENTAL API.
+
+    Attributes:
+      code: A StatusCode object to be sent to the client.
+      details: A UTF-8-encodable string to be sent to the client upon
+        termination of the RPC.
+      trailing_metadata: The trailing :term:`metadata` in the RPC.
+    """
+
+
+#############################  gRPC Exceptions  ################################
+
+
+class RpcError(Exception):
+    """Raised by the gRPC library to indicate non-OK-status RPC termination."""
+
+
+##############################  Shared Context  ################################
+
+
+class RpcContext(abc.ABC):
+    """Provides RPC-related information and action."""
+
+    @abc.abstractmethod
+    def is_active(self):
+        """Describes whether the RPC is active or has terminated.
+
+        Returns:
+          bool:
+          True if RPC is active, False otherwise.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def time_remaining(self):
+        """Describes the length of allowed time remaining for the RPC.
+
+        Returns:
+          A nonnegative float indicating the length of allowed time in seconds
+          remaining for the RPC to complete before it is considered to have
+          timed out, or None if no deadline was specified for the RPC.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def cancel(self):
+        """Cancels the RPC.
+
+        Idempotent and has no effect if the RPC has already terminated.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def add_callback(self, callback):
+        """Registers a callback to be called on RPC termination.
+
+        Args:
+          callback: A no-parameter callable to be called on RPC termination.
+
+        Returns:
+          True if the callback was added and will be called later; False if
+            the callback was not added and will not be called (because the RPC
+            already terminated or some other reason).
+        """
+        raise NotImplementedError()
+
+
+#########################  Invocation-Side Context  ############################
+
+
+class Call(RpcContext, metaclass=abc.ABCMeta):
+    """Invocation-side utility object for an RPC."""
+
+    @abc.abstractmethod
+    def initial_metadata(self):
+        """Accesses the initial metadata sent by the server.
+
+        This method blocks until the value is available.
+
+        Returns:
+          The initial :term:`metadata`.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def trailing_metadata(self):
+        """Accesses the trailing metadata sent by the server.
+
+        This method blocks until the value is available.
+
+        Returns:
+          The trailing :term:`metadata`.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def code(self):
+        """Accesses the status code sent by the server.
+
+        This method blocks until the value is available.
+
+        Returns:
+          The StatusCode value for the RPC.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def details(self):
+        """Accesses the details sent by the server.
+
+        This method blocks until the value is available.
+
+        Returns:
+          The details string of the RPC.
+        """
+        raise NotImplementedError()
+
+
+##############  Invocation-Side Interceptor Interfaces & Classes  ##############
+
+
+class ClientCallDetails(abc.ABC):
+    """Describes an RPC to be invoked.
+
+    Attributes:
+      method: The method name of the RPC.
+      timeout: An optional duration of time in seconds to allow for the RPC.
+      metadata: Optional :term:`metadata` to be transmitted to
+        the service-side of the RPC.
+      credentials: An optional CallCredentials for the RPC.
+      wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
+      compression: An element of grpc.compression, e.g.
+        grpc.compression.Gzip.
+    """
+
+
+class UnaryUnaryClientInterceptor(abc.ABC):
+    """Affords intercepting unary-unary invocations."""
+
+    @abc.abstractmethod
+    def intercept_unary_unary(self, continuation, client_call_details, request):
+        """Intercepts a unary-unary invocation asynchronously.
+
+        Args:
+          continuation: A function that proceeds with the invocation by
+            executing the next interceptor in chain or invoking the
+            actual RPC on the underlying Channel. It is the interceptor's
+            responsibility to call it if it decides to move the RPC forward.
+            The interceptor can use
+            `response_future = continuation(client_call_details, request)`
+            to continue with the RPC. `continuation` returns an object that is
+            both a Call for the RPC and a Future. In the event of RPC
+            completion, the return Call-Future's result value will be
+            the response message of the RPC. Should the event terminate
+            with non-OK status, the returned Call-Future's exception value
+            will be an RpcError.
+          client_call_details: A ClientCallDetails object describing the
+            outgoing RPC.
+          request: The request value for the RPC.
+
+        Returns:
+            An object that is both a Call for the RPC and a Future.
+            In the event of RPC completion, the return Call-Future's
+            result value will be the response message of the RPC.
+            Should the event terminate with non-OK status, the returned
+            Call-Future's exception value will be an RpcError.
+        """
+        raise NotImplementedError()
+
+
+class UnaryStreamClientInterceptor(abc.ABC):
+    """Affords intercepting unary-stream invocations."""
+
+    @abc.abstractmethod
+    def intercept_unary_stream(
+        self, continuation, client_call_details, request
+    ):
+        """Intercepts a unary-stream invocation.
+
+        Args:
+          continuation: A function that proceeds with the invocation by
+            executing the next interceptor in chain or invoking the
+            actual RPC on the underlying Channel. It is the interceptor's
+            responsibility to call it if it decides to move the RPC forward.
+            The interceptor can use
+            `response_iterator = continuation(client_call_details, request)`
+            to continue with the RPC. `continuation` returns an object that is
+            both a Call for the RPC and an iterator for response values.
+            Drawing response values from the returned Call-iterator may
+            raise RpcError indicating termination of the RPC with non-OK
+            status.
+          client_call_details: A ClientCallDetails object describing the
+            outgoing RPC.
+          request: The request value for the RPC.
+
+        Returns:
+            An object that is both a Call for the RPC and an iterator of
+            response values. Drawing response values from the returned
+            Call-iterator may raise RpcError indicating termination of
+            the RPC with non-OK status. This object *should* also fulfill the
+            Future interface, though it may not.
+        """
+        raise NotImplementedError()
+
+
+class StreamUnaryClientInterceptor(abc.ABC):
+    """Affords intercepting stream-unary invocations."""
+
+    @abc.abstractmethod
+    def intercept_stream_unary(
+        self, continuation, client_call_details, request_iterator
+    ):
+        """Intercepts a stream-unary invocation asynchronously.
+
+        Args:
+          continuation: A function that proceeds with the invocation by
+            executing the next interceptor in chain or invoking the
+            actual RPC on the underlying Channel. It is the interceptor's
+            responsibility to call it if it decides to move the RPC forward.
+            The interceptor can use
+            `response_future = continuation(client_call_details, request_iterator)`
+            to continue with the RPC. `continuation` returns an object that is
+            both a Call for the RPC and a Future. In the event of RPC completion,
+            the return Call-Future's result value will be the response message
+            of the RPC. Should the event terminate with non-OK status, the
+            returned Call-Future's exception value will be an RpcError.
+          client_call_details: A ClientCallDetails object describing the
+            outgoing RPC.
+          request_iterator: An iterator that yields request values for the RPC.
+
+        Returns:
+          An object that is both a Call for the RPC and a Future.
+          In the event of RPC completion, the return Call-Future's
+          result value will be the response message of the RPC.
+          Should the event terminate with non-OK status, the returned
+          Call-Future's exception value will be an RpcError.
+        """
+        raise NotImplementedError()
+
+
+class StreamStreamClientInterceptor(abc.ABC):
+    """Affords intercepting stream-stream invocations."""
+
+    @abc.abstractmethod
+    def intercept_stream_stream(
+        self, continuation, client_call_details, request_iterator
+    ):
+        """Intercepts a stream-stream invocation.
+
+        Args:
+          continuation: A function that proceeds with the invocation by
+            executing the next interceptor in chain or invoking the
+            actual RPC on the underlying Channel. It is the interceptor's
+            responsibility to call it if it decides to move the RPC forward.
+            The interceptor can use
+            `response_iterator = continuation(client_call_details, request_iterator)`
+            to continue with the RPC. `continuation` returns an object that is
+            both a Call for the RPC and an iterator for response values.
+            Drawing response values from the returned Call-iterator may
+            raise RpcError indicating termination of the RPC with non-OK
+            status.
+          client_call_details: A ClientCallDetails object describing the
+            outgoing RPC.
+          request_iterator: An iterator that yields request values for the RPC.
+
+        Returns:
+          An object that is both a Call for the RPC and an iterator of
+          response values. Drawing response values from the returned
+          Call-iterator may raise RpcError indicating termination of
+          the RPC with non-OK status. This object *should* also fulfill the
+          Future interface, though it may not.
+        """
+        raise NotImplementedError()
+
+
+############  Authentication & Authorization Interfaces & Classes  #############
+
+
+class ChannelCredentials(object):
+    """An encapsulation of the data required to create a secure Channel.
+
+    This class has no supported interface - it exists to define the type of its
+    instances and its instances exist to be passed to other functions. For
+    example, ssl_channel_credentials returns an instance of this class and
+    secure_channel requires an instance of this class.
+    """
+
+    def __init__(self, credentials):
+        self._credentials = credentials
+
+
+class CallCredentials(object):
+    """An encapsulation of the data required to assert an identity over a call.
+
+    A CallCredentials has to be used with secure Channel, otherwise the
+    metadata will not be transmitted to the server.
+
+    A CallCredentials may be composed with ChannelCredentials to always assert
+    identity for every call over that Channel.
+
+    This class has no supported interface - it exists to define the type of its
+    instances and its instances exist to be passed to other functions.
+    """
+
+    def __init__(self, credentials):
+        self._credentials = credentials
+
+
+class AuthMetadataContext(abc.ABC):
+    """Provides information to call credentials metadata plugins.
+
+    Attributes:
+      service_url: A string URL of the service being called into.
+      method_name: A string of the fully qualified method name being called.
+    """
+
+
+class AuthMetadataPluginCallback(abc.ABC):
+    """Callback object received by a metadata plugin."""
+
+    def __call__(self, metadata, error):
+        """Passes to the gRPC runtime authentication metadata for an RPC.
+
+        Args:
+          metadata: The :term:`metadata` used to construct the CallCredentials.
+          error: An Exception to indicate error or None to indicate success.
+        """
+        raise NotImplementedError()
+
+
+class AuthMetadataPlugin(abc.ABC):
+    """A specification for custom authentication."""
+
+    def __call__(self, context, callback):
+        """Implements authentication by passing metadata to a callback.
+
+        This method will be invoked asynchronously in a separate thread.
+
+        Args:
+          context: An AuthMetadataContext providing information on the RPC that
+            the plugin is being called to authenticate.
+          callback: An AuthMetadataPluginCallback to be invoked either
+            synchronously or asynchronously.
+        """
+        raise NotImplementedError()
+
+
+class ServerCredentials(object):
+    """An encapsulation of the data required to open a secure port on a Server.
+
+    This class has no supported interface - it exists to define the type of its
+    instances and its instances exist to be passed to other functions.
+    """
+
+    def __init__(self, credentials):
+        self._credentials = credentials
+
+
+class ServerCertificateConfiguration(object):
+    """A certificate configuration for use with an SSL-enabled Server.
+
+    Instances of this class can be returned in the certificate configuration
+    fetching callback.
+
+    This class has no supported interface -- it exists to define the
+    type of its instances and its instances exist to be passed to
+    other functions.
+    """
+
+    def __init__(self, certificate_configuration):
+        self._certificate_configuration = certificate_configuration
+
+
+########################  Multi-Callable Interfaces  ###########################
+
+
+class UnaryUnaryMultiCallable(abc.ABC):
+    """Affords invoking a unary-unary RPC from client-side."""
+
+    @abc.abstractmethod
+    def __call__(
+        self,
+        request,
+        timeout=None,
+        metadata=None,
+        credentials=None,
+        wait_for_ready=None,
+        compression=None,
+    ):
+        """Synchronously invokes the underlying RPC.
+
+        Args:
+          request: The request value for the RPC.
+          timeout: An optional duration of time in seconds to allow
+            for the RPC.
+          metadata: Optional :term:`metadata` to be transmitted to the
+            service-side of the RPC.
+          credentials: An optional CallCredentials for the RPC. Only valid for
+            secure Channel.
+          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
+          compression: An element of grpc.compression, e.g.
+            grpc.compression.Gzip.
+
+        Returns:
+          The response value for the RPC.
+
+        Raises:
+          RpcError: Indicating that the RPC terminated with non-OK status. The
+            raised RpcError will also be a Call for the RPC affording the RPC's
+            metadata, status code, and details.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def with_call(
+        self,
+        request,
+        timeout=None,
+        metadata=None,
+        credentials=None,
+        wait_for_ready=None,
+        compression=None,
+    ):
+        """Synchronously invokes the underlying RPC.
+
+        Args:
+          request: The request value for the RPC.
+          timeout: An optional durating of time in seconds to allow for
+            the RPC.
+          metadata: Optional :term:`metadata` to be transmitted to the
+            service-side of the RPC.
+          credentials: An optional CallCredentials for the RPC. Only valid for
+            secure Channel.
+          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
+          compression: An element of grpc.compression, e.g.
+            grpc.compression.Gzip.
+
+        Returns:
+          The response value for the RPC and a Call value for the RPC.
+
+        Raises:
+          RpcError: Indicating that the RPC terminated with non-OK status. The
+            raised RpcError will also be a Call for the RPC affording the RPC's
+            metadata, status code, and details.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def future(
+        self,
+        request,
+        timeout=None,
+        metadata=None,
+        credentials=None,
+        wait_for_ready=None,
+        compression=None,
+    ):
+        """Asynchronously invokes the underlying RPC.
+
+        Args:
+          request: The request value for the RPC.
+          timeout: An optional duration of time in seconds to allow for
+            the RPC.
+          metadata: Optional :term:`metadata` to be transmitted to the
+            service-side of the RPC.
+          credentials: An optional CallCredentials for the RPC. Only valid for
+            secure Channel.
+          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
+          compression: An element of grpc.compression, e.g.
+            grpc.compression.Gzip.
+
+        Returns:
+            An object that is both a Call for the RPC and a Future.
+            In the event of RPC completion, the return Call-Future's result
+            value will be the response message of the RPC.
+            Should the event terminate with non-OK status,
+            the returned Call-Future's exception value will be an RpcError.
+        """
+        raise NotImplementedError()
+
+
+class UnaryStreamMultiCallable(abc.ABC):
+    """Affords invoking a unary-stream RPC from client-side."""
+
+    @abc.abstractmethod
+    def __call__(
+        self,
+        request,
+        timeout=None,
+        metadata=None,
+        credentials=None,
+        wait_for_ready=None,
+        compression=None,
+    ):
+        """Invokes the underlying RPC.
+
+        Args:
+          request: The request value for the RPC.
+          timeout: An optional duration of time in seconds to allow for
+            the RPC. If None, the timeout is considered infinite.
+          metadata: An optional :term:`metadata` to be transmitted to the
+            service-side of the RPC.
+          credentials: An optional CallCredentials for the RPC. Only valid for
+            secure Channel.
+          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
+          compression: An element of grpc.compression, e.g.
+            grpc.compression.Gzip.
+
+        Returns:
+            An object that is a Call for the RPC, an iterator of response
+            values, and a Future for the RPC. Drawing response values from the
+            returned Call-iterator may raise RpcError indicating termination of
+            the RPC with non-OK status.
+        """
+        raise NotImplementedError()
+
+
+class StreamUnaryMultiCallable(abc.ABC):
+    """Affords invoking a stream-unary RPC from client-side."""
+
+    @abc.abstractmethod
+    def __call__(
+        self,
+        request_iterator,
+        timeout=None,
+        metadata=None,
+        credentials=None,
+        wait_for_ready=None,
+        compression=None,
+    ):
+        """Synchronously invokes the underlying RPC.
+
+        Args:
+          request_iterator: An iterator that yields request values for
+            the RPC.
+          timeout: An optional duration of time in seconds to allow for
+            the RPC. If None, the timeout is considered infinite.
+          metadata: Optional :term:`metadata` to be transmitted to the
+            service-side of the RPC.
+          credentials: An optional CallCredentials for the RPC. Only valid for
+            secure Channel.
+          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
+          compression: An element of grpc.compression, e.g.
+            grpc.compression.Gzip.
+
+        Returns:
+          The response value for the RPC.
+
+        Raises:
+          RpcError: Indicating that the RPC terminated with non-OK status. The
+            raised RpcError will also implement grpc.Call, affording methods
+            such as metadata, code, and details.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def with_call(
+        self,
+        request_iterator,
+        timeout=None,
+        metadata=None,
+        credentials=None,
+        wait_for_ready=None,
+        compression=None,
+    ):
+        """Synchronously invokes the underlying RPC on the client.
+
+        Args:
+          request_iterator: An iterator that yields request values for
+            the RPC.
+          timeout: An optional duration of time in seconds to allow for
+            the RPC. If None, the timeout is considered infinite.
+          metadata: Optional :term:`metadata` to be transmitted to the
+            service-side of the RPC.
+          credentials: An optional CallCredentials for the RPC. Only valid for
+            secure Channel.
+          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
+          compression: An element of grpc.compression, e.g.
+            grpc.compression.Gzip.
+
+        Returns:
+          The response value for the RPC and a Call object for the RPC.
+
+        Raises:
+          RpcError: Indicating that the RPC terminated with non-OK status. The
+            raised RpcError will also be a Call for the RPC affording the RPC's
+            metadata, status code, and details.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def future(
+        self,
+        request_iterator,
+        timeout=None,
+        metadata=None,
+        credentials=None,
+        wait_for_ready=None,
+        compression=None,
+    ):
+        """Asynchronously invokes the underlying RPC on the client.
+
+        Args:
+          request_iterator: An iterator that yields request values for the RPC.
+          timeout: An optional duration of time in seconds to allow for
+            the RPC. If None, the timeout is considered infinite.
+          metadata: Optional :term:`metadata` to be transmitted to the
+            service-side of the RPC.
+          credentials: An optional CallCredentials for the RPC. Only valid for
+            secure Channel.
+          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
+          compression: An element of grpc.compression, e.g.
+            grpc.compression.Gzip.
+
+        Returns:
+            An object that is both a Call for the RPC and a Future.
+            In the event of RPC completion, the return Call-Future's result value
+            will be the response message of the RPC. Should the event terminate
+            with non-OK status, the returned Call-Future's exception value will
+            be an RpcError.
+        """
+        raise NotImplementedError()
+
+
+class StreamStreamMultiCallable(abc.ABC):
+    """Affords invoking a stream-stream RPC on client-side."""
+
+    @abc.abstractmethod
+    def __call__(
+        self,
+        request_iterator,
+        timeout=None,
+        metadata=None,
+        credentials=None,
+        wait_for_ready=None,
+        compression=None,
+    ):
+        """Invokes the underlying RPC on the client.
+
+        Args:
+          request_iterator: An iterator that yields request values for the RPC.
+          timeout: An optional duration of time in seconds to allow for
+            the RPC. If not specified, the timeout is considered infinite.
+          metadata: Optional :term:`metadata` to be transmitted to the
+            service-side of the RPC.
+          credentials: An optional CallCredentials for the RPC. Only valid for
+            secure Channel.
+          wait_for_ready: An optional flag to enable :term:`wait_for_ready` mechanism.
+          compression: An element of grpc.compression, e.g.
+            grpc.compression.Gzip.
+
+        Returns:
+            An object that is a Call for the RPC, an iterator of response
+            values, and a Future for the RPC. Drawing response values from the
+            returned Call-iterator may raise RpcError indicating termination of
+            the RPC with non-OK status.
+        """
+        raise NotImplementedError()
+
+
+#############################  Channel Interface  ##############################
+
+
+class Channel(abc.ABC):
+    """Affords RPC invocation via generic methods on client-side.
+
+    Channel objects implement the Context Manager type, although they need not
+    support being entered and exited multiple times.
+    """
+
+    @abc.abstractmethod
+    def subscribe(self, callback, try_to_connect=False):
+        """Subscribe to this Channel's connectivity state machine.
+
+        A Channel may be in any of the states described by ChannelConnectivity.
+        This method allows application to monitor the state transitions.
+        The typical use case is to debug or gain better visibility into gRPC
+        runtime's state.
+
+        Args:
+          callback: A callable to be invoked with ChannelConnectivity argument.
+            ChannelConnectivity describes current state of the channel.
+            The callable will be invoked immediately upon subscription
+            and again for every change to ChannelConnectivity until it
+            is unsubscribed or this Channel object goes out of scope.
+          try_to_connect: A boolean indicating whether or not this Channel
+            should attempt to connect immediately. If set to False, gRPC
+            runtime decides when to connect.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def unsubscribe(self, callback):
+        """Unsubscribes a subscribed callback from this Channel's connectivity.
+
+        Args:
+          callback: A callable previously registered with this Channel from
+          having been passed to its "subscribe" method.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def unary_unary(
+        self,
+        method,
+        request_serializer=None,
+        response_deserializer=None,
+        _registered_method=False,
+    ):
+        """Creates a UnaryUnaryMultiCallable for a unary-unary method.
+
+        Args:
+          method: The name of the RPC method.
+          request_serializer: Optional :term:`serializer` for serializing the request
+            message. Request goes unserialized in case None is passed.
+          response_deserializer: Optional :term:`deserializer` for deserializing the
+            response message. Response goes undeserialized in case None
+            is passed.
+          _registered_method: Implementation Private. A bool representing whether the method
+            is registered.
+
+        Returns:
+          A UnaryUnaryMultiCallable value for the named unary-unary method.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def unary_stream(
+        self,
+        method,
+        request_serializer=None,
+        response_deserializer=None,
+        _registered_method=False,
+    ):
+        """Creates a UnaryStreamMultiCallable for a unary-stream method.
+
+        Args:
+          method: The name of the RPC method.
+          request_serializer: Optional :term:`serializer` for serializing the request
+            message. Request goes unserialized in case None is passed.
+          response_deserializer: Optional :term:`deserializer` for deserializing the
+            response message. Response goes undeserialized in case None is
+            passed.
+          _registered_method: Implementation Private. A bool representing whether the method
+            is registered.
+
+        Returns:
+          A UnaryStreamMultiCallable value for the name unary-stream method.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def stream_unary(
+        self,
+        method,
+        request_serializer=None,
+        response_deserializer=None,
+        _registered_method=False,
+    ):
+        """Creates a StreamUnaryMultiCallable for a stream-unary method.
+
+        Args:
+          method: The name of the RPC method.
+          request_serializer: Optional :term:`serializer` for serializing the request
+            message. Request goes unserialized in case None is passed.
+          response_deserializer: Optional :term:`deserializer` for deserializing the
+            response message. Response goes undeserialized in case None is
+            passed.
+          _registered_method: Implementation Private. A bool representing whether the method
+            is registered.
+
+        Returns:
+          A StreamUnaryMultiCallable value for the named stream-unary method.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def stream_stream(
+        self,
+        method,
+        request_serializer=None,
+        response_deserializer=None,
+        _registered_method=False,
+    ):
+        """Creates a StreamStreamMultiCallable for a stream-stream method.
+
+        Args:
+          method: The name of the RPC method.
+          request_serializer: Optional :term:`serializer` for serializing the request
+            message. Request goes unserialized in case None is passed.
+          response_deserializer: Optional :term:`deserializer` for deserializing the
+            response message. Response goes undeserialized in case None
+            is passed.
+          _registered_method: Implementation Private. A bool representing whether the method
+            is registered.
+
+        Returns:
+          A StreamStreamMultiCallable value for the named stream-stream method.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def close(self):
+        """Closes this Channel and releases all resources held by it.
+
+        Closing the Channel will immediately terminate all RPCs active with the
+        Channel and it is not valid to invoke new RPCs with the Channel.
+
+        This method is idempotent.
+        """
+        raise NotImplementedError()
+
+    def __enter__(self):
+        """Enters the runtime context related to the channel object."""
+        raise NotImplementedError()
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        """Exits the runtime context related to the channel object."""
+        raise NotImplementedError()
+
+
+##########################  Service-Side Context  ##############################
+
+
+class ServicerContext(RpcContext, metaclass=abc.ABCMeta):
+    """A context object passed to method implementations."""
+
+    @abc.abstractmethod
+    def invocation_metadata(self):
+        """Accesses the metadata sent by the client.
+
+        Returns:
+          The invocation :term:`metadata`.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def peer(self):
+        """Identifies the peer that invoked the RPC being serviced.
+
+        Returns:
+          A string identifying the peer that invoked the RPC being serviced.
+          The string format is determined by gRPC runtime.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def peer_identities(self):
+        """Gets one or more peer identity(s).
+
+        Equivalent to
+        servicer_context.auth_context().get(servicer_context.peer_identity_key())
+
+        Returns:
+          An iterable of the identities, or None if the call is not
+          authenticated. Each identity is returned as a raw bytes type.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def peer_identity_key(self):
+        """The auth property used to identify the peer.
+
+        For example, "x509_common_name" or "x509_subject_alternative_name" are
+        used to identify an SSL peer.
+
+        Returns:
+          The auth property (string) that indicates the
+          peer identity, or None if the call is not authenticated.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def auth_context(self):
+        """Gets the auth context for the call.
+
+        Returns:
+          A map of strings to an iterable of bytes for each auth property.
+        """
+        raise NotImplementedError()
+
+    def set_compression(self, compression):
+        """Set the compression algorithm to be used for the entire call.
+
+        Args:
+          compression: An element of grpc.compression, e.g.
+            grpc.compression.Gzip.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def send_initial_metadata(self, initial_metadata):
+        """Sends the initial metadata value to the client.
+
+        This method need not be called by implementations if they have no
+        metadata to add to what the gRPC runtime will transmit.
+
+        Args:
+          initial_metadata: The initial :term:`metadata`.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def set_trailing_metadata(self, trailing_metadata):
+        """Sets the trailing metadata for the RPC.
+
+        Sets the trailing metadata to be sent upon completion of the RPC.
+
+        If this method is invoked multiple times throughout the lifetime of an
+        RPC, the value supplied in the final invocation will be the value sent
+        over the wire.
+
+        This method need not be called by implementations if they have no
+        metadata to add to what the gRPC runtime will transmit.
+
+        Args:
+          trailing_metadata: The trailing :term:`metadata`.
+        """
+        raise NotImplementedError()
+
+    def trailing_metadata(self):
+        """Access value to be used as trailing metadata upon RPC completion.
+
+        This is an EXPERIMENTAL API.
+
+        Returns:
+          The trailing :term:`metadata` for the RPC.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def abort(self, code, details):
+        """Raises an exception to terminate the RPC with a non-OK status.
+
+        The code and details passed as arguments will supersede any existing
+        ones.
+
+        Args:
+          code: A StatusCode object to be sent to the client.
+            It must not be StatusCode.OK.
+          details: A UTF-8-encodable string to be sent to the client upon
+            termination of the RPC.
+
+        Raises:
+          Exception: An exception is always raised to signal the abortion the
+            RPC to the gRPC runtime.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def abort_with_status(self, status):
+        """Raises an exception to terminate the RPC with a non-OK status.
+
+        The status passed as argument will supersede any existing status code,
+        status message and trailing metadata.
+
+        This is an EXPERIMENTAL API.
+
+        Args:
+          status: A grpc.Status object. The status code in it must not be
+            StatusCode.OK.
+
+        Raises:
+          Exception: An exception is always raised to signal the abortion the
+            RPC to the gRPC runtime.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def set_code(self, code):
+        """Sets the value to be used as status code upon RPC completion.
+
+        This method need not be called by method implementations if they wish
+        the gRPC runtime to determine the status code of the RPC.
+
+        Args:
+          code: A StatusCode object to be sent to the client.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def set_details(self, details):
+        """Sets the value to be used as detail string upon RPC completion.
+
+        This method need not be called by method implementations if they have
+        no details to transmit.
+
+        Args:
+          details: A UTF-8-encodable string to be sent to the client upon
+            termination of the RPC.
+        """
+        raise NotImplementedError()
+
+    def code(self):
+        """Accesses the value to be used as status code upon RPC completion.
+
+        This is an EXPERIMENTAL API.
+
+        Returns:
+          The StatusCode value for the RPC.
+        """
+        raise NotImplementedError()
+
+    def details(self):
+        """Accesses the value to be used as detail string upon RPC completion.
+
+        This is an EXPERIMENTAL API.
+
+        Returns:
+          The details string of the RPC.
+        """
+        raise NotImplementedError()
+
+    def disable_next_message_compression(self):
+        """Disables compression for the next response message.
+
+        This method will override any compression configuration set during
+        server creation or set on the call.
+        """
+        raise NotImplementedError()
+
+
+#####################  Service-Side Handler Interfaces  ########################
+
+
+class RpcMethodHandler(abc.ABC):
+    """An implementation of a single RPC method.
+
+    Attributes:
+      request_streaming: Whether the RPC supports exactly one request message
+        or any arbitrary number of request messages.
+      response_streaming: Whether the RPC supports exactly one response message
+        or any arbitrary number of response messages.
+      request_deserializer: A callable :term:`deserializer` that accepts a byte string and
+        returns an object suitable to be passed to this object's business
+        logic, or None to indicate that this object's business logic should be
+        passed the raw request bytes.
+      response_serializer: A callable :term:`serializer` that accepts an object produced
+        by this object's business logic and returns a byte string, or None to
+        indicate that the byte strings produced by this object's business logic
+        should be transmitted on the wire as they are.
+      unary_unary: This object's application-specific business logic as a
+        callable value that takes a request value and a ServicerContext object
+        and returns a response value. Only non-None if both request_streaming
+        and response_streaming are False.
+      unary_stream: This object's application-specific business logic as a
+        callable value that takes a request value and a ServicerContext object
+        and returns an iterator of response values. Only non-None if
+        request_streaming is False and response_streaming is True.
+      stream_unary: This object's application-specific business logic as a
+        callable value that takes an iterator of request values and a
+        ServicerContext object and returns a response value. Only non-None if
+        request_streaming is True and response_streaming is False.
+      stream_stream: This object's application-specific business logic as a
+        callable value that takes an iterator of request values and a
+        ServicerContext object and returns an iterator of response values.
+        Only non-None if request_streaming and response_streaming are both
+        True.
+    """
+
+
+class HandlerCallDetails(abc.ABC):
+    """Describes an RPC that has just arrived for service.
+
+    Attributes:
+      method: The method name of the RPC.
+      invocation_metadata: The :term:`metadata` sent by the client.
+    """
+
+
+class GenericRpcHandler(abc.ABC):
+    """An implementation of arbitrarily many RPC methods."""
+
+    @abc.abstractmethod
+    def service(self, handler_call_details):
+        """Returns the handler for servicing the RPC.
+
+        Args:
+          handler_call_details: A HandlerCallDetails describing the RPC.
+
+        Returns:
+          An RpcMethodHandler with which the RPC may be serviced if the
+          implementation chooses to service this RPC, or None otherwise.
+        """
+        raise NotImplementedError()
+
+
+class ServiceRpcHandler(GenericRpcHandler, metaclass=abc.ABCMeta):
+    """An implementation of RPC methods belonging to a service.
+
+    A service handles RPC methods with structured names of the form
+    '/Service.Name/Service.Method', where 'Service.Name' is the value
+    returned by service_name(), and 'Service.Method' is the method
+    name.  A service can have multiple method names, but only a single
+    service name.
+    """
+
+    @abc.abstractmethod
+    def service_name(self):
+        """Returns this service's name.
+
+        Returns:
+          The service name.
+        """
+        raise NotImplementedError()
+
+
+####################  Service-Side Interceptor Interfaces  #####################
+
+
+class ServerInterceptor(abc.ABC):
+    """Affords intercepting incoming RPCs on the service-side."""
+
+    @abc.abstractmethod
+    def intercept_service(self, continuation, handler_call_details):
+        """Intercepts incoming RPCs before handing them over to a handler.
+
+        State can be passed from an interceptor to downstream interceptors
+        via contextvars. The first interceptor is called from an empty
+        contextvars.Context, and the same Context is used for downstream
+        interceptors and for the final handler call. Note that there are no
+        guarantees that interceptors and handlers will be called from the
+        same thread.
+
+        Args:
+          continuation: A function that takes a HandlerCallDetails and
+            proceeds to invoke the next interceptor in the chain, if any,
+            or the RPC handler lookup logic, with the call details passed
+            as an argument, and returns an RpcMethodHandler instance if
+            the RPC is considered serviced, or None otherwise.
+          handler_call_details: A HandlerCallDetails describing the RPC.
+
+        Returns:
+          An RpcMethodHandler with which the RPC may be serviced if the
+          interceptor chooses to service this RPC, or None otherwise.
+        """
+        raise NotImplementedError()
+
+
+#############################  Server Interface  ###############################
+
+
+class Server(abc.ABC):
+    """Services RPCs."""
+
+    @abc.abstractmethod
+    def add_generic_rpc_handlers(self, generic_rpc_handlers):
+        """Registers GenericRpcHandlers with this Server.
+
+        This method is only safe to call before the server is started.
+
+        Args:
+          generic_rpc_handlers: An iterable of GenericRpcHandlers that will be
+          used to service RPCs.
+        """
+        raise NotImplementedError()
+
+    def add_registered_method_handlers(self, service_name, method_handlers):
+        """Registers GenericRpcHandlers with this Server.
+
+        This method is only safe to call before the server is started.
+
+        If the same method have both generic and registered handler,
+        registered handler will take precedence.
+
+        Args:
+          service_name: The service name.
+          method_handlers: A dictionary that maps method names to corresponding
+            RpcMethodHandler.
+        """
+
+    @abc.abstractmethod
+    def add_insecure_port(self, address):
+        """Opens an insecure port for accepting RPCs.
+
+        This method may only be called before starting the server.
+
+        Args:
+          address: The address for which to open a port. If the port is 0,
+            or not specified in the address, then gRPC runtime will choose a port.
+
+        Returns:
+          An integer port on which server will accept RPC requests.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def add_secure_port(self, address, server_credentials):
+        """Opens a secure port for accepting RPCs.
+
+        This method may only be called before starting the server.
+
+        Args:
+          address: The address for which to open a port.
+            if the port is 0, or not specified in the address, then gRPC
+            runtime will choose a port.
+          server_credentials: A ServerCredentials object.
+
+        Returns:
+          An integer port on which server will accept RPC requests.
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def start(self):
+        """Starts this Server.
+
+        This method may only be called once. (i.e. it is not idempotent).
+        """
+        raise NotImplementedError()
+
+    @abc.abstractmethod
+    def stop(self, grace):
+        """Stops this Server.
+
+        This method immediately stop service of new RPCs in all cases.
+
+        If a grace period is specified, this method waits until all active
+        RPCs are finished or until the grace period is reached. RPCs that haven't
+        been terminated within the grace period are aborted.
+        If a grace period is not specified (by passing None for `grace`),
+        all existing RPCs are aborted immediately and this method
+        blocks until the last RPC handler terminates.
+
+        This method is idempotent and may be called at any time.
+        Passing a smaller grace value in a subsequent call will have
+        the effect of stopping the Server sooner (passing None will
+        have the effect of stopping the server immediately). Passing
+        a larger grace value in a subsequent call *will not* have the
+        effect of stopping the server later (i.e. the most restrictive
+        grace value is used).
+
+        Args:
+          grace: A duration of time in seconds or None.
+
+        Returns:
+          A threading.Event that will be set when this Server has completely
+          stopped, i.e. when running RPCs either complete or are aborted and
+          all handlers have terminated.
+        """
+        raise NotImplementedError()
+
+    def wait_for_termination(self, timeout=None):
+        """Block current thread until the server stops.
+
+        This is an EXPERIMENTAL API.
+
+        The wait will not consume computational resources during blocking, and
+        it will block until one of the two following conditions are met:
+
+        1) The server is stopped or terminated;
+        2) A timeout occurs if timeout is not `None`.
+
+        The timeout argument works in the same way as `threading.Event.wait()`.
+        https://docs.python.org/3/library/threading.html#threading.Event.wait
+
+        Args:
+          timeout: A floating point number specifying a timeout for the
+            operation in seconds.
+
+        Returns:
+          A bool indicates if the operation times out.
+        """
+        raise NotImplementedError()
+
+
+#################################  Functions    ################################
+
+
+def unary_unary_rpc_method_handler(
+    behavior, request_deserializer=None, response_serializer=None
+):
+    """Creates an RpcMethodHandler for a unary-unary RPC method.
+
+    Args:
+      behavior: The implementation of an RPC that accepts one request
+        and returns one response.
+      request_deserializer: An optional :term:`deserializer` for request deserialization.
+      response_serializer: An optional :term:`serializer` for response serialization.
+
+    Returns:
+      An RpcMethodHandler object that is typically used by grpc.Server.
+    """
+    from grpc import _utilities  # pylint: disable=cyclic-import
+
+    return _utilities.RpcMethodHandler(
+        False,
+        False,
+        request_deserializer,
+        response_serializer,
+        behavior,
+        None,
+        None,
+        None,
+    )
+
+
+def unary_stream_rpc_method_handler(
+    behavior, request_deserializer=None, response_serializer=None
+):
+    """Creates an RpcMethodHandler for a unary-stream RPC method.
+
+    Args:
+      behavior: The implementation of an RPC that accepts one request
+        and returns an iterator of response values.
+      request_deserializer: An optional :term:`deserializer` for request deserialization.
+      response_serializer: An optional :term:`serializer` for response serialization.
+
+    Returns:
+      An RpcMethodHandler object that is typically used by grpc.Server.
+    """
+    from grpc import _utilities  # pylint: disable=cyclic-import
+
+    return _utilities.RpcMethodHandler(
+        False,
+        True,
+        request_deserializer,
+        response_serializer,
+        None,
+        behavior,
+        None,
+        None,
+    )
+
+
+def stream_unary_rpc_method_handler(
+    behavior, request_deserializer=None, response_serializer=None
+):
+    """Creates an RpcMethodHandler for a stream-unary RPC method.
+
+    Args:
+      behavior: The implementation of an RPC that accepts an iterator of
+        request values and returns a single response value.
+      request_deserializer: An optional :term:`deserializer` for request deserialization.
+      response_serializer: An optional :term:`serializer` for response serialization.
+
+    Returns:
+      An RpcMethodHandler object that is typically used by grpc.Server.
+    """
+    from grpc import _utilities  # pylint: disable=cyclic-import
+
+    return _utilities.RpcMethodHandler(
+        True,
+        False,
+        request_deserializer,
+        response_serializer,
+        None,
+        None,
+        behavior,
+        None,
+    )
+
+
+def stream_stream_rpc_method_handler(
+    behavior, request_deserializer=None, response_serializer=None
+):
+    """Creates an RpcMethodHandler for a stream-stream RPC method.
+
+    Args:
+      behavior: The implementation of an RPC that accepts an iterator of
+        request values and returns an iterator of response values.
+      request_deserializer: An optional :term:`deserializer` for request deserialization.
+      response_serializer: An optional :term:`serializer` for response serialization.
+
+    Returns:
+      An RpcMethodHandler object that is typically used by grpc.Server.
+    """
+    from grpc import _utilities  # pylint: disable=cyclic-import
+
+    return _utilities.RpcMethodHandler(
+        True,
+        True,
+        request_deserializer,
+        response_serializer,
+        None,
+        None,
+        None,
+        behavior,
+    )
+
+
+def method_handlers_generic_handler(service, method_handlers):
+    """Creates a GenericRpcHandler from RpcMethodHandlers.
+
+    Args:
+      service: The name of the service that is implemented by the
+        method_handlers.
+      method_handlers: A dictionary that maps method names to corresponding
+        RpcMethodHandler.
+
+    Returns:
+      A GenericRpcHandler. This is typically added to the grpc.Server object
+      with add_generic_rpc_handlers() before starting the server.
+    """
+    from grpc import _utilities  # pylint: disable=cyclic-import
+
+    return _utilities.DictionaryGenericHandler(service, method_handlers)
+
+
+def ssl_channel_credentials(
+    root_certificates=None, private_key=None, certificate_chain=None
+):
+    """Creates a ChannelCredentials for use with an SSL-enabled Channel.
+
+    Args:
+      root_certificates: The PEM-encoded root certificates as a byte string,
+        or None to retrieve them from a default location chosen by gRPC
+        runtime.
+      private_key: The PEM-encoded private key as a byte string, or None if no
+        private key should be used.
+      certificate_chain: The PEM-encoded certificate chain as a byte string
+        to use or None if no certificate chain should be used.
+
+    Returns:
+      A ChannelCredentials for use with an SSL-enabled Channel.
+    """
+    return ChannelCredentials(
+        _cygrpc.SSLChannelCredentials(
+            root_certificates, private_key, certificate_chain
+        )
+    )
+
+
+def xds_channel_credentials(fallback_credentials=None):
+    """Creates a ChannelCredentials for use with xDS. This is an EXPERIMENTAL
+      API.
+
+    Args:
+      fallback_credentials: Credentials to use in case it is not possible to
+        establish a secure connection via xDS. If no fallback_credentials
+        argument is supplied, a default SSLChannelCredentials is used.
+    """
+    fallback_credentials = (
+        ssl_channel_credentials()
+        if fallback_credentials is None
+        else fallback_credentials
+    )
+    return ChannelCredentials(
+        _cygrpc.XDSChannelCredentials(fallback_credentials._credentials)
+    )
+
+
+def metadata_call_credentials(metadata_plugin, name=None):
+    """Construct CallCredentials from an AuthMetadataPlugin.
+
+    Args:
+      metadata_plugin: An AuthMetadataPlugin to use for authentication.
+      name: An optional name for the plugin.
+
+    Returns:
+      A CallCredentials.
+    """
+    from grpc import _plugin_wrapping  # pylint: disable=cyclic-import
+
+    return _plugin_wrapping.metadata_plugin_call_credentials(
+        metadata_plugin, name
+    )
+
+
+def access_token_call_credentials(access_token):
+    """Construct CallCredentials from an access token.
+
+    Args:
+      access_token: A string to place directly in the http request
+        authorization header, for example
+        "authorization: Bearer <access_token>".
+
+    Returns:
+      A CallCredentials.
+    """
+    from grpc import _auth  # pylint: disable=cyclic-import
+    from grpc import _plugin_wrapping  # pylint: disable=cyclic-import
+
+    return _plugin_wrapping.metadata_plugin_call_credentials(
+        _auth.AccessTokenAuthMetadataPlugin(access_token), None
+    )
+
+
+def composite_call_credentials(*call_credentials):
+    """Compose multiple CallCredentials to make a new CallCredentials.
+
+    Args:
+      *call_credentials: At least two CallCredentials objects.
+
+    Returns:
+      A CallCredentials object composed of the given CallCredentials objects.
+    """
+    return CallCredentials(
+        _cygrpc.CompositeCallCredentials(
+            tuple(
+                single_call_credentials._credentials
+                for single_call_credentials in call_credentials
+            )
+        )
+    )
+
+
+def composite_channel_credentials(channel_credentials, *call_credentials):
+    """Compose a ChannelCredentials and one or more CallCredentials objects.
+
+    Args:
+      channel_credentials: A ChannelCredentials object.
+      *call_credentials: One or more CallCredentials objects.
+
+    Returns:
+      A ChannelCredentials composed of the given ChannelCredentials and
+        CallCredentials objects.
+    """
+    return ChannelCredentials(
+        _cygrpc.CompositeChannelCredentials(
+            tuple(
+                single_call_credentials._credentials
+                for single_call_credentials in call_credentials
+            ),
+            channel_credentials._credentials,
+        )
+    )
+
+
+def ssl_server_credentials(
+    private_key_certificate_chain_pairs,
+    root_certificates=None,
+    require_client_auth=False,
+):
+    """Creates a ServerCredentials for use with an SSL-enabled Server.
+
+    Args:
+      private_key_certificate_chain_pairs: A list of pairs of the form
+        [PEM-encoded private key, PEM-encoded certificate chain].
+      root_certificates: An optional byte string of PEM-encoded client root
+        certificates that the server will use to verify client authentication.
+        If omitted, require_client_auth must also be False.
+      require_client_auth: A boolean indicating whether or not to require
+        clients to be authenticated. May only be True if root_certificates
+        is not None.
+
+    Returns:
+      A ServerCredentials for use with an SSL-enabled Server. Typically, this
+      object is an argument to add_secure_port() method during server setup.
+    """
+    if not private_key_certificate_chain_pairs:
+        raise ValueError(
+            "At least one private key-certificate chain pair is required!"
+        )
+    elif require_client_auth and root_certificates is None:
+        raise ValueError(
+            "Illegal to require client auth without providing root"
+            " certificates!"
+        )
+    else:
+        return ServerCredentials(
+            _cygrpc.server_credentials_ssl(
+                root_certificates,
+                [
+                    _cygrpc.SslPemKeyCertPair(key, pem)
+                    for key, pem in private_key_certificate_chain_pairs
+                ],
+                require_client_auth,
+            )
+        )
+
+
+def xds_server_credentials(fallback_credentials):
+    """Creates a ServerCredentials for use with xDS. This is an EXPERIMENTAL
+      API.
+
+    Args:
+      fallback_credentials: Credentials to use in case it is not possible to
+        establish a secure connection via xDS. No default value is provided.
+    """
+    return ServerCredentials(
+        _cygrpc.xds_server_credentials(fallback_credentials._credentials)
+    )
+
+
+def insecure_server_credentials():
+    """Creates a credentials object directing the server to use no credentials.
+      This is an EXPERIMENTAL API.
+
+    This object cannot be used directly in a call to `add_secure_port`.
+    Instead, it should be used to construct other credentials objects, e.g.
+    with xds_server_credentials.
+    """
+    return ServerCredentials(_cygrpc.insecure_server_credentials())
+
+
+def ssl_server_certificate_configuration(
+    private_key_certificate_chain_pairs, root_certificates=None
+):
+    """Creates a ServerCertificateConfiguration for use with a Server.
+
+    Args:
+      private_key_certificate_chain_pairs: A collection of pairs of
+        the form [PEM-encoded private key, PEM-encoded certificate
+        chain].
+      root_certificates: An optional byte string of PEM-encoded client root
+        certificates that the server will use to verify client authentication.
+
+    Returns:
+      A ServerCertificateConfiguration that can be returned in the certificate
+        configuration fetching callback.
+    """
+    if private_key_certificate_chain_pairs:
+        return ServerCertificateConfiguration(
+            _cygrpc.server_certificate_config_ssl(
+                root_certificates,
+                [
+                    _cygrpc.SslPemKeyCertPair(key, pem)
+                    for key, pem in private_key_certificate_chain_pairs
+                ],
+            )
+        )
+    else:
+        raise ValueError(
+            "At least one private key-certificate chain pair is required!"
+        )
+
+
+def dynamic_ssl_server_credentials(
+    initial_certificate_configuration,
+    certificate_configuration_fetcher,
+    require_client_authentication=False,
+):
+    """Creates a ServerCredentials for use with an SSL-enabled Server.
+
+    Args:
+      initial_certificate_configuration (ServerCertificateConfiguration): The
+        certificate configuration with which the server will be initialized.
+      certificate_configuration_fetcher (callable): A callable that takes no
+        arguments and should return a ServerCertificateConfiguration to
+        replace the server's current certificate, or None for no change
+        (i.e., the server will continue its current certificate
+        config). The library will call this callback on *every* new
+        client connection before starting the TLS handshake with the
+        client, thus allowing the user application to optionally
+        return a new ServerCertificateConfiguration that the server will then
+        use for the handshake.
+      require_client_authentication: A boolean indicating whether or not to
+        require clients to be authenticated.
+
+    Returns:
+      A ServerCredentials.
+    """
+    return ServerCredentials(
+        _cygrpc.server_credentials_ssl_dynamic_cert_config(
+            initial_certificate_configuration,
+            certificate_configuration_fetcher,
+            require_client_authentication,
+        )
+    )
+
+
+@enum.unique
+class LocalConnectionType(enum.Enum):
+    """Types of local connection for local credential creation.
+
+    Attributes:
+      UDS: Unix domain socket connections
+      LOCAL_TCP: Local TCP connections.
+    """
+
+    UDS = _cygrpc.LocalConnectionType.uds
+    LOCAL_TCP = _cygrpc.LocalConnectionType.local_tcp
+
+
+def local_channel_credentials(local_connect_type=LocalConnectionType.LOCAL_TCP):
+    """Creates a local ChannelCredentials used for local connections.
+
+    This is an EXPERIMENTAL API.
+
+    Local credentials are used by local TCP endpoints (e.g. localhost:10000)
+    also UDS connections.
+
+    The connections created by local channel credentials are not
+    encrypted, but will be checked if they are local or not.
+    The UDS connections are considered secure by providing peer authentication
+    and data confidentiality while TCP connections are considered insecure.
+
+    It is allowed to transmit call credentials over connections created by
+    local channel credentials.
+
+    Local channel credentials are useful for 1) eliminating insecure_channel usage;
+    2) enable unit testing for call credentials without setting up secrets.
+
+    Args:
+      local_connect_type: Local connection type (either
+        grpc.LocalConnectionType.UDS or grpc.LocalConnectionType.LOCAL_TCP)
+
+    Returns:
+      A ChannelCredentials for use with a local Channel
+    """
+    return ChannelCredentials(
+        _cygrpc.channel_credentials_local(local_connect_type.value)
+    )
+
+
+def local_server_credentials(local_connect_type=LocalConnectionType.LOCAL_TCP):
+    """Creates a local ServerCredentials used for local connections.
+
+    This is an EXPERIMENTAL API.
+
+    Local credentials are used by local TCP endpoints (e.g. localhost:10000)
+    also UDS connections.
+
+    The connections created by local server credentials are not
+    encrypted, but will be checked if they are local or not.
+    The UDS connections are considered secure by providing peer authentication
+    and data confidentiality while TCP connections are considered insecure.
+
+    It is allowed to transmit call credentials over connections created by local
+    server credentials.
+
+    Local server credentials are useful for 1) eliminating insecure_channel usage;
+    2) enable unit testing for call credentials without setting up secrets.
+
+    Args:
+      local_connect_type: Local connection type (either
+        grpc.LocalConnectionType.UDS or grpc.LocalConnectionType.LOCAL_TCP)
+
+    Returns:
+      A ServerCredentials for use with a local Server
+    """
+    return ServerCredentials(
+        _cygrpc.server_credentials_local(local_connect_type.value)
+    )
+
+
+def alts_channel_credentials(service_accounts=None):
+    """Creates a ChannelCredentials for use with an ALTS-enabled Channel.
+
+    This is an EXPERIMENTAL API.
+    ALTS credentials API can only be used in GCP environment as it relies on
+    handshaker service being available. For more info about ALTS see
+    https://cloud.google.com/security/encryption-in-transit/application-layer-transport-security
+
+    Args:
+      service_accounts: A list of server identities accepted by the client.
+        If target service accounts are provided and none of them matches the
+        peer identity of the server, handshake will fail. The arg can be empty
+        if the client does not have any information about trusted server
+        identity.
+    Returns:
+      A ChannelCredentials for use with an ALTS-enabled Channel
+    """
+    return ChannelCredentials(
+        _cygrpc.channel_credentials_alts(service_accounts or [])
+    )
+
+
+def alts_server_credentials():
+    """Creates a ServerCredentials for use with an ALTS-enabled connection.
+
+    This is an EXPERIMENTAL API.
+    ALTS credentials API can only be used in GCP environment as it relies on
+    handshaker service being available. For more info about ALTS see
+    https://cloud.google.com/security/encryption-in-transit/application-layer-transport-security
+
+    Returns:
+      A ServerCredentials for use with an ALTS-enabled Server
+    """
+    return ServerCredentials(_cygrpc.server_credentials_alts())
+
+
+def compute_engine_channel_credentials(call_credentials):
+    """Creates a compute engine channel credential.
+
+    This credential can only be used in a GCP environment as it relies on
+    a handshaker service. For more info about ALTS, see
+    https://cloud.google.com/security/encryption-in-transit/application-layer-transport-security
+
+    This channel credential is expected to be used as part of a composite
+    credential in conjunction with a call credentials that authenticates the
+    VM's default service account. If used with any other sort of call
+    credential, the connection may suddenly and unexpectedly begin failing RPCs.
+    """
+    return ChannelCredentials(
+        _cygrpc.channel_credentials_compute_engine(
+            call_credentials._credentials
+        )
+    )
+
+
+def channel_ready_future(channel):
+    """Creates a Future that tracks when a Channel is ready.
+
+    Cancelling the Future does not affect the channel's state machine.
+    It merely decouples the Future from channel state machine.
+
+    Args:
+      channel: A Channel object.
+
+    Returns:
+      A Future object that matures when the channel connectivity is
+      ChannelConnectivity.READY.
+    """
+    from grpc import _utilities  # pylint: disable=cyclic-import
+
+    return _utilities.channel_ready_future(channel)
+
+
+def insecure_channel(target, options=None, compression=None):
+    """Creates an insecure Channel to a server.
+
+    The returned Channel is thread-safe.
+
+    Args:
+      target: The server address
+      options: An optional list of key-value pairs (:term:`channel_arguments`
+        in gRPC Core runtime) to configure the channel.
+      compression: An optional value indicating the compression method to be
+        used over the lifetime of the channel.
+
+    Returns:
+      A Channel.
+    """
+    from grpc import _channel  # pylint: disable=cyclic-import
+
+    return _channel.Channel(
+        target, () if options is None else options, None, compression
+    )
+
+
+def secure_channel(target, credentials, options=None, compression=None):
+    """Creates a secure Channel to a server.
+
+    The returned Channel is thread-safe.
+
+    Args:
+      target: The server address.
+      credentials: A ChannelCredentials instance.
+      options: An optional list of key-value pairs (:term:`channel_arguments`
+        in gRPC Core runtime) to configure the channel.
+      compression: An optional value indicating the compression method to be
+        used over the lifetime of the channel.
+
+    Returns:
+      A Channel.
+    """
+    from grpc import _channel  # pylint: disable=cyclic-import
+    from grpc.experimental import _insecure_channel_credentials
+
+    if credentials._credentials is _insecure_channel_credentials:
+        raise ValueError(
+            "secure_channel cannot be called with insecure credentials."
+            + " Call insecure_channel instead."
+        )
+    return _channel.Channel(
+        target,
+        () if options is None else options,
+        credentials._credentials,
+        compression,
+    )
+
+
+def intercept_channel(channel, *interceptors):
+    """Intercepts a channel through a set of interceptors.
+
+    Args:
+      channel: A Channel.
+      interceptors: Zero or more objects of type
+        UnaryUnaryClientInterceptor,
+        UnaryStreamClientInterceptor,
+        StreamUnaryClientInterceptor, or
+        StreamStreamClientInterceptor.
+        Interceptors are given control in the order they are listed.
+
+    Returns:
+      A Channel that intercepts each invocation via the provided interceptors.
+
+    Raises:
+      TypeError: If interceptor does not derive from any of
+        UnaryUnaryClientInterceptor,
+        UnaryStreamClientInterceptor,
+        StreamUnaryClientInterceptor, or
+        StreamStreamClientInterceptor.
+    """
+    from grpc import _interceptor  # pylint: disable=cyclic-import
+
+    return _interceptor.intercept_channel(channel, *interceptors)
+
+
+def server(
+    thread_pool,
+    handlers=None,
+    interceptors=None,
+    options=None,
+    maximum_concurrent_rpcs=None,
+    compression=None,
+    xds=False,
+):
+    """Creates a Server with which RPCs can be serviced.
+
+    Args:
+      thread_pool: A futures.ThreadPoolExecutor to be used by the Server
+        to execute RPC handlers.
+      handlers: An optional list of GenericRpcHandlers used for executing RPCs.
+        More handlers may be added by calling add_generic_rpc_handlers any time
+        before the server is started.
+      interceptors: An optional list of ServerInterceptor objects that observe
+        and optionally manipulate the incoming RPCs before handing them over to
+        handlers. The interceptors are given control in the order they are
+        specified. This is an EXPERIMENTAL API.
+      options: An optional list of key-value pairs (:term:`channel_arguments` in gRPC runtime)
+        to configure the channel.
+      maximum_concurrent_rpcs: The maximum number of concurrent RPCs this server
+        will service before returning RESOURCE_EXHAUSTED status, or None to
+        indicate no limit.
+      compression: An element of grpc.compression, e.g.
+        grpc.compression.Gzip. This compression algorithm will be used for the
+        lifetime of the server unless overridden.
+      xds: If set to true, retrieves server configuration via xDS. This is an
+        EXPERIMENTAL option.
+
+    Returns:
+      A Server object.
+    """
+    from grpc import _server  # pylint: disable=cyclic-import
+
+    return _server.create_server(
+        thread_pool,
+        () if handlers is None else handlers,
+        () if interceptors is None else interceptors,
+        () if options is None else options,
+        maximum_concurrent_rpcs,
+        compression,
+        xds,
+    )
+
+
+@contextlib.contextmanager
+def _create_servicer_context(rpc_event, state, request_deserializer):
+    from grpc import _server  # pylint: disable=cyclic-import
+
+    context = _server._Context(rpc_event, state, request_deserializer)
+    yield context
+    context._finalize_state()  # pylint: disable=protected-access
+
+
+@enum.unique
+class Compression(enum.IntEnum):
+    """Indicates the compression method to be used for an RPC.
+
+    Attributes:
+     NoCompression: Do not use compression algorithm.
+     Deflate: Use "Deflate" compression algorithm.
+     Gzip: Use "Gzip" compression algorithm.
+    """
+
+    NoCompression = _compression.NoCompression
+    Deflate = _compression.Deflate
+    Gzip = _compression.Gzip
+
+
+###################################  __all__  #################################
+
+__all__ = (
+    "FutureTimeoutError",
+    "FutureCancelledError",
+    "Future",
+    "ChannelConnectivity",
+    "StatusCode",
+    "Status",
+    "RpcError",
+    "RpcContext",
+    "Call",
+    "ChannelCredentials",
+    "CallCredentials",
+    "AuthMetadataContext",
+    "AuthMetadataPluginCallback",
+    "AuthMetadataPlugin",
+    "Compression",
+    "ClientCallDetails",
+    "ServerCertificateConfiguration",
+    "ServerCredentials",
+    "LocalConnectionType",
+    "UnaryUnaryMultiCallable",
+    "UnaryStreamMultiCallable",
+    "StreamUnaryMultiCallable",
+    "StreamStreamMultiCallable",
+    "UnaryUnaryClientInterceptor",
+    "UnaryStreamClientInterceptor",
+    "StreamUnaryClientInterceptor",
+    "StreamStreamClientInterceptor",
+    "Channel",
+    "ServicerContext",
+    "RpcMethodHandler",
+    "HandlerCallDetails",
+    "GenericRpcHandler",
+    "ServiceRpcHandler",
+    "Server",
+    "ServerInterceptor",
+    "unary_unary_rpc_method_handler",
+    "unary_stream_rpc_method_handler",
+    "stream_unary_rpc_method_handler",
+    "stream_stream_rpc_method_handler",
+    "method_handlers_generic_handler",
+    "ssl_channel_credentials",
+    "metadata_call_credentials",
+    "access_token_call_credentials",
+    "composite_call_credentials",
+    "composite_channel_credentials",
+    "compute_engine_channel_credentials",
+    "local_channel_credentials",
+    "local_server_credentials",
+    "alts_channel_credentials",
+    "alts_server_credentials",
+    "ssl_server_credentials",
+    "ssl_server_certificate_configuration",
+    "dynamic_ssl_server_credentials",
+    "channel_ready_future",
+    "insecure_channel",
+    "secure_channel",
+    "intercept_channel",
+    "server",
+    "protos",
+    "services",
+    "protos_and_services",
+    "xds_channel_credentials",
+    "xds_server_credentials",
+    "insecure_server_credentials",
+)
+
+############################### Extension Shims ################################
+
+# Here to maintain backwards compatibility; avoid using these in new code!
+try:
+    import grpc_tools
+
+    sys.modules.update({"grpc.tools": grpc_tools})
+except ImportError:
+    pass
+try:
+    import grpc_health
+
+    sys.modules.update({"grpc.health": grpc_health})
+except ImportError:
+    pass
+try:
+    import grpc_reflection
+
+    sys.modules.update({"grpc.reflection": grpc_reflection})
+except ImportError:
+    pass
+
+# Prevents import order issue in the case of renamed path.
+if sys.version_info >= (3, 6) and __name__ == "grpc":
+    from grpc import aio  # pylint: disable=ungrouped-imports
+
+    sys.modules.update({"grpc.aio": aio})