Adding Fast tokenizers for SentencePiece based tokenizers - Breaking: remove Transfo-XL fast tokenizer (#7141)

* [WIP] SP tokenizers

* fixing tests for T5

* WIP tokenizers

* serialization

* update T5

* WIP T5 tokenization

* slow to fast conversion script

* Refactoring to move tokenzier implementations inside transformers

* Adding gpt - refactoring - quality

* WIP adding several tokenizers to the fast world

* WIP Roberta - moving implementations

* update to dev4 switch file loading to in-memory loading

* Updating and fixing

* advancing on the tokenizers - updating do_lower_case

* style and quality

* moving forward with tokenizers conversion and tests

* MBart, T5

* dumping the fast version of transformer XL

* Adding to autotokenizers + style/quality

* update init and space_between_special_tokens

* style and quality

* bump up tokenizers version

* add protobuf

* fix pickle Bert JP with Mecab

* fix newly added tokenizers

* style and quality

* fix bert japanese

* fix funnel

* limite tokenizer warning to one occurence

* clean up file

* fix new tokenizers

* fast tokenizers deep tests

* WIP adding all the special fast tests on the new fast tokenizers

* quick fix

* adding more fast tokenizers in the fast tests

* all tokenizers in fast version tested

* Adding BertGenerationFast

* bump up setup.py for CI

* remove BertGenerationFast (too early)

* bump up tokenizers version

* Clean old docstrings

* Typo

* Update following Lysandre comments

Co-authored-by: Sylvain Gugger <sylvain.gugger@gmail.com>

tests/test_tokenization_xlnet.py

@@ -18,7 +18,7 @@ import os
 import unittest
 
 from transformers.testing_utils import slow
-from transformers.tokenization_xlnet import SPIECE_UNDERLINE, XLNetTokenizer
+from transformers.tokenization_xlnet import SPIECE_UNDERLINE, XLNetTokenizer, XLNetTokenizerFast
 
 from .test_tokenization_common import TokenizerTesterMixin
 
@@ -29,12 +29,15 @@ SAMPLE_VOCAB = os.path.join(os.path.dirname(os.path.abspath(__file__)), "fixture
 class XLNetTokenizationTest(TokenizerTesterMixin, unittest.TestCase):
 
     tokenizer_class = XLNetTokenizer
+    rust_tokenizer_class = XLNetTokenizerFast
+    test_rust_tokenizer = True
 
     def setUp(self):
         super().setUp()
 
         # We have a SentencePiece fixture for testing
         tokenizer = XLNetTokenizer(SAMPLE_VOCAB, keep_accents=True)
+        tokenizer.sanitize_special_tokens()
         tokenizer.save_pretrained(self.tmpdirname)
 
     def test_full_tokenizer(self):