LED (#9278)

* create model

* add integration

* save current state

* make integration tests pass

* add one more test

* add explanation to tests

* remove from bart

* add padding

* remove unnecessary test

* make all tests pass

* re-add cookie cutter tests

* finish PyTorch

* fix attention test

* Update tests/test_modeling_common.py

* revert change

* remove unused file

* add string to doc

* save intermediate

* make tf integration tests pass

* finish tf

* fix doc

* fix docs again

* add led to doctree

* add to auto tokenizer

* added tips for led

* make style

* apply jplus statements

* correct tf longformer

* apply lysandres suggestions

* apply sylvains suggestions

* Apply suggestions from code review

src/transformers/utils/dummy_tokenizers_objects.py

@@ -128,6 +128,15 @@ class LayoutLMTokenizerFast:
         requires_tokenizers(self)
 
 
+class LEDTokenizerFast:
+    def __init__(self, *args, **kwargs):
+        requires_tokenizers(self)
+
+    @classmethod
+    def from_pretrained(self, *args, **kwargs):
+        requires_tokenizers(self)
+
+
 class LongformerTokenizerFast:
     def __init__(self, *args, **kwargs):
         requires_tokenizers(self)