- Updated the fetch_refseq_sequence function to handle HTTP errors more robustly by distinguishing between urllib and requests exceptions.
- Added input validation to skip empty or NaN RefSeq IDs.
- Cleaned up whitespace and comma-separated values from the RefSeq ID.
- Enhanced error messages for better debugging.
- Updated exception handling in _fetch_sequence_for_row to accommodate new error handling in fetch_refseq_sequence.