## Summary
- Add `create_import_stub()` helper to `embeddings/utils.py` for
handling optional dependencies
- Fix MLX doctest collection failures by using import stubs in
`gte_mlx_model.py`
- Module now imports successfully for doctest collection even when MLX
is not installed
## Changes
- **New utility function**: `create_import_stub()` creates placeholder
objects that allow class inheritance but raise helpful errors when used
- **Updated MLX model**: Uses import stubs instead of direct imports
that fail immediately
- **Graceful degradation**: Clear error messages when MLX functionality
is accessed without MLX installed
## Test Results
- ✅ `pytest --doctest-modules python/lancedb` now passes (with and
without MLX installed)
- ✅ All existing tests continue to pass
- ✅ MLX functionality works normally when MLX is installed
- ✅ Helpful error messages when MLX functionality is used without MLX
installed
Fixes#2538
---------
Co-authored-by: Will Jones <willjones127@gmail.com>
