Starts asynchronous cancellation on a long-running operation.  The server
        makes a best effort to cancel the operation, but success is not
        guaranteed.  If the server doesn't support this method, it returns
        ``google.rpc.Code.UNIMPLEMENTED``.  Clients can use
        ``Operations.GetOperation`` or
        other methods to check whether the cancellation succeeded or whether the
        operation completed despite cancellation. On successful cancellation,
        the operation is not deleted; instead, it becomes an operation with
        an ``Operation.error`` value with a ``google.rpc.Status.code`` of 1,
        corresponding to ``Code.CANCELLED``.

        Example:
          >>> from google.gapic.longrunning import operations_client
          >>> api = operations_client.OperationsClient()
          >>> name = ''
          >>> api.cancel_operation(name)

        Args:
          name (string): The name of the operation resource to be cancelled.
          options (:class:`google.gax.CallOptions`): Overrides the default
            settings for this call, e.g, timeout, retries etc.

        Raises:
          :exc:`google.gax.errors.GaxError` if the RPC is aborted.
          :exc:`ValueError` if the parameters are invalid.

def cancel_operation(self, name, options=None):
        """
        Starts asynchronous cancellation on a long-running operation.  The server
        makes a best effort to cancel the operation, but success is not
        guaranteed.  If the server doesn't support this method, it returns
        ``google.rpc.Code.UNIMPLEMENTED``.  Clients can use
        ``Operations.GetOperation`` or
        other methods to check whether the cancellation succeeded or whether the
        operation completed despite cancellation. On successful cancellation,
        the operation is not deleted; instead, it becomes an operation with
        an ``Operation.error`` value with a ``google.rpc.Status.code`` of 1,
        corresponding to ``Code.CANCELLED``.

        Example:
          >>> from google.gapic.longrunning import operations_client
          >>> api = operations_client.OperationsClient()
          >>> name = ''
          >>> api.cancel_operation(name)

        Args:
          name (string): The name of the operation resource to be cancelled.
          options (:class:`google.gax.CallOptions`): Overrides the default
            settings for this call, e.g, timeout, retries etc.

        Raises:
          :exc:`google.gax.errors.GaxError` if the RPC is aborted.
          :exc:`ValueError` if the parameters are invalid.
        """
        # Create the request object.
        request = operations_pb2.CancelOperationRequest(name=name)
        self._cancel_operation(request, options)