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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:
 async def with_call(self, request_iterator, timeout=None, metadata=None, credentials=None):
 """Synchronously invokes the underlying RPC on the client. Args: request_iterator: An ASYNC 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. 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. """

        fut = self.future(request_iterator, timeout, metadata, credentials)
        try:
            result = await fut
            return (result, fut)
        finally:
            if not fut.done():
                fut.cancel()