Apply suggestion from @h-mayorquin

See related issue NeuralEnsemble#1817

Author: ree-gupta

neo/rawio/tdtrawio.py

@@ -288,7 +288,12 @@ def _parse_header(self):
                         block_path = self.dirname / segment_name
                         sev_regex = f"{tankname}_{segment_name}_{stream_name}_[cC]h{chan_id}.sev"
                         sev_filename = list(block_path.glob(sev_regex))
-                        sev_filename = sev_filename[0] if len(sev_filename) == 1 else None
+if len(sev_filename) == 1:
+    sev_filename = sev_filename[0]
+elif len(sev_filename) == 0:
+    sev_filename = None   # Indirect flag for TEV Format, see issue 1087
+else:
+    raise ValueError(f"Multiple SEV files matched for channel {chan_id}: {sev_filename}")
                     else:
                         # for single block datasets the exact name of sev files is not known
                         sev_regex = f"*_[cC]h{chan_id}.sev"