Modular: support for importing functions from any file (#35692)

* fix function imports

* improve comment

* Update modeling_switch_function.py

* make checks more robust

* improvement

* rename

* final test update

examples/modular-transformers/modeling_new_task_model.py

@@ -107,7 +107,6 @@ class NewTaskModelPreTrainedModel(PreTrainedModel):
     _supports_cache_class = True
     _supports_quantized_cache = True
     _supports_static_cache = True
-    _supports_cache_class = True
     _supports_flash_attn_2 = True
     _supports_sdpa = True