def _aggregation_pipeline(self):
        """Return the full aggregation pipeline for this ChangeStream."""
        options = self._change_stream_options()
        full_pipeline = [{'$changeStream': options}]
        full_pipeline.extend(self._pipeline)
        return full_pipeline
Return the full aggregation pipeline for this ChangeStream.
stackoverflow/venv/lib/python3.6/site-packages/pymongo/change_stream.py