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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 _commit(self):
 """Transactionally commit the changes accumulated. Returns: List[google.cloud.proto.firestore.v1beta1.\ to the changes committed, returned in the same order as the changes were applied to this transaction. A write result contains an ``update_time`` field. Raises: ValueError: If no transaction is in progress. """

        if not self.in_progress:
            raise ValueError(_CANT_COMMIT)

        commit_response = _commit_with_retry(self._client, self._write_pbs, self._id)

        self._clean_up()
        return list(commit_response.write_results)