transformers

725f4ad1 - Add tie_weights() to LM heads and set bias in set_output_embeddings() (#28948)

Add tie_weights() to LM heads and set bias in set_output_embeddings() (#28948) * Add tie_weights() to LM heads and set bias in set_output_embeddings() The bias were not tied correctly in some LM heads, and this change should fix that. * Moving test_save_and_load_low_cpu_mem_usage to ModelTesterMixin * Adding _tie_weights() to MPNet and Vilt * Skip test for low cpu mem usage for Deta/DeformableDetr since they cannot init on meta device * Rename to test name to save_load to match the convention