add where copied from

src/transformers/integrations/accelerate.py

@@ -15,6 +15,9 @@
 Since, https://github.com/huggingface/transformers/pull/36963, loading is always performed with models on meta
 device. But since the `init_empty_weights` and `find_tied_parameters` functions are from accelerate, and accelerate is
 somewhat still a soft dependency, we copy the functions here to be used natively in Transformers.
+
+The `init_empty_weights` and `init_on_device` functions were copied from `accelerate.big_modeling.py`, and the
+`find_tied_parameters` was copied from `accelerate.utils.modeling.py`
 """
 
 import warnings