fix error

Author: samuelgarcia

neo/rawio/openephysrawio.py

@@ -168,7 +168,7 @@ def _parse_header(self):
         signal_channels['stream_id'] = chan_stream_ids
 
         # and create streams channels (keep natural order 'CH' first)
-        stream_ids, order = np.unique(chan_stream_ids)
+        stream_ids, order = np.unique(chan_stream_ids, return_index=True)
         stream_ids = stream_ids[order]
         signal_streams = [(f'Signals {stream_id}', f'{stream_id}') for stream_id in stream_ids]
         signal_streams = np.array(signal_streams, dtype=_signal_stream_dtype)