transformers 5.x introduced two breaking changes that affect the
bundled GroundingDINO BertModelWarper:
1. `BertModel.get_head_mask()` was removed. Added a standalone
`_get_head_mask()` fallback with a `hasattr` check so both
transformers 4.x and 5.x work.
2. `BertModel.get_extended_attention_mask()` changed its 3rd
positional argument from `device` to `dtype`. The old call-site
passes a `torch.device`, which newer transformers interprets as
`dtype=torch.device` → TypeError. Replaced with a standalone
`_get_extended_attention_mask()` static method that also handles
PyTorch 2.9's prohibition of `1.0 - bool_tensor` by explicitly
casting to float32 first.
Fixes#140
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
