TRL 0.22.x checks _is_vlm (model type) instead of _is_vision_dataset
(dataset content, added in 0.25.1+) in _set_signature_columns_if_needed.
When _is_vlm=True (e.g. Gemma3), signature columns are set to vision-only
["messages","prompt","completion","images"], which has zero overlap with
tokenized text columns [input_ids, labels, attention_mask, ...], causing
a ValueError.
Fix: expand the VLM branch signature columns to include both vision and
text column names. Extra columns not present in the dataset are harmlessly
ignored by _remove_unused_columns (it only raises when zero columns match).
Co-authored-by: Daniel Hanchen <danielhanchen@users.noreply.github.com>
52e35bbfd7