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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 _consume_single_get(response_iterator):
 """Consume a gRPC stream that should contain a single response. The stream will correspond to a ``BatchGetDocuments`` request made for a single document. Args: response_iterator (~google.cloud.exceptions.GrpcRendezvous):
 A streaming iterator returned from a ``BatchGetDocuments`` request. Returns: ~google.cloud.proto.firestore.v1beta1.\ firestore_pb2.BatchGetDocumentsResponse: The single "get" response in the batch. Raises: ValueError: If anything other than exactly one response is returned. """

    # Calling ``list()`` consumes the entire iterator.
    all_responses = list(response_iterator)
    if len(all_responses) != 1:
        raise ValueError(
            "Unexpected response from `BatchGetDocumentsResponse`",
            all_responses,
            "Expected only one result",
        )

    return all_responses[0]