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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 get_file_stream_api(self):
 """This creates a new file pusher thread. Call start to initiate the thread that talks to W&B"""

        if not self._file_stream_api:
            if self._current_run_id is None:
                raise UsageError(
                    'Must have a current run to use file stream API.')
            self._file_stream_api = FileStreamApi(self, self._current_run_id)
        return self._file_stream_api