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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_instance( self, parent, instance_id, instance, retry=google.api_core.gapic_v1.method.DEFAULT, timeout=google.api_core.gapic_v1.method.DEFAULT, metadata=None, ):
 """ Creates an instance and begins preparing it to begin serving. The returned ``long-running operation`` can be used to track the progress of preparing the new instance. The instance name is assigned by the caller. If the named instance already exists, ``CreateInstance`` returns ``ALREADY_EXISTS``. Immediately upon completion of this request: - The instance is readable via the API, with all requested attributes but no allocated resources. Its state is ``CREATING``. Until completion of the returned operation: - Cancelling the operation renders the instance immediately unreadable via the API. - The instance can be deleted. - All other attempts to modify the instance are rejected. Upon completion of the returned operation: - Billing for all successfully-allocated resources begins (some types may have lower than the requested levels). - Databases can be created in the instance. - The instance's allocated resource levels are readable via the API. - The instance's state becomes ``READY``. The returned ``long-running operation`` will have a name of the format ``<instance_name>/operations/<operation_id>`` and can be used to track creation of the instance. The ``metadata`` field type is ``CreateInstanceMetadata``. The ``response`` field type is ``Instance``, if successful. Example: Args: parent (str):
 Required. The name of the project in which to create the instance. Values are of the form ``projects/<project>``. instance_id (str):
 Required. The ID of the instance to create. Valid identifiers are of the form ``[a-z][-a-z0-9]*[a-z0-9]`` and must be between 6 and 30 characters in length. instance (Union[dict, ~google.cloud.spanner_admin_instance_v1.types.Instance]):
 Required. The instance to create. The name may be omitted, but if specified must be ``<parent>/instances/<instance_id>``. If a dict is provided, it must be of the same form as the protobuf message :class:`~google.cloud.spanner_admin_instance_v1.types.Instance` retry (Optional[google.api_core.retry.Retry]):
 A retry object used to retry requests. If ``None`` is specified, requests will not be retried. timeout (Optional[float]):
 The amount of time, in seconds, to wait for the request to complete. Note that if ``retry`` is specified, the timeout applies to each individual attempt. metadata (Optional[Sequence[Tuple[str, str]]]):
 Additional metadata that is provided to the method. Returns: A :class:`~google.cloud.spanner_admin_instance_v1.types._OperationFuture` instance. Raises: google.api_core.exceptions.GoogleAPICallError: If the request failed for any reason. google.api_core.exceptions.RetryError: If the request failed due to a retryable error and retry attempts failed. ValueError: If the parameters are invalid. """

        # Wrap the transport method to add retry and timeout logic.
        if "create_instance" not in self._inner_api_calls:
            self._inner_api_calls[
                "create_instance"
            ] = google.api_core.gapic_v1.method.wrap_method(
                self.transport.create_instance,
                default_retry=self._method_configs["CreateInstance"].retry,
                default_timeout=self._method_configs["CreateInstance"].timeout,
                client_info=self._client_info,
            )

        request = spanner_instance_admin_pb2.CreateInstanceRequest(
            parent=parent, instance_id=instance_id, instance=instance
        )
        if metadata is None:
            metadata = []
        metadata = list(metadata)
        try:
            routing_header = [("parent", parent)]
        except AttributeError:
            pass
        else:
            routing_metadata = google.api_core.gapic_v1.routing_header.to_grpc_metadata(
                routing_header
            )
            metadata.append(routing_metadata)

        operation = self._inner_api_calls["create_instance"](
            request, retry=retry, timeout=timeout, metadata=metadata
        )
        return google.api_core.operation.from_gapic(
            operation,
            self.transport._operations_client,
            spanner_instance_admin_pb2.Instance,
            metadata_type=spanner_instance_admin_pb2.CreateInstanceMetadata,
        )