MT5 should have an autotokenizer (#8743)

* MT5 should have an autotokenizer

* Different configurations should be able to point to same tokenizers

src/transformers/models/auto/tokenization_auto.py

@@ -72,6 +72,7 @@ from .configuration_auto import (
     MarianConfig,
     MBartConfig,
     MobileBertConfig,
+    MT5Config,
     OpenAIGPTConfig,
     PegasusConfig,
     ProphetNetConfig,
@@ -173,6 +174,7 @@ TOKENIZER_MAPPING = OrderedDict(
     [
         (RetriBertConfig, (RetriBertTokenizer, RetriBertTokenizerFast)),
         (T5Config, (T5Tokenizer, T5TokenizerFast)),
+        (MT5Config, (T5Tokenizer, T5TokenizerFast)),
         (MobileBertConfig, (MobileBertTokenizer, MobileBertTokenizerFast)),
         (DistilBertConfig, (DistilBertTokenizer, DistilBertTokenizerFast)),
         (AlbertConfig, (AlbertTokenizer, AlbertTokenizerFast)),

tests/test_tokenization_auto.py

@@ -99,21 +99,13 @@ class AutoTokenizerTest(unittest.TestCase):
 
         for mapping in mappings:
             mapping = tuple(mapping.items())
-            for index, (child_config, (child_model_py, child_model_fast)) in enumerate(mapping[1:]):
-                for parent_config, (parent_model_py, parent_model_fast) in mapping[: index + 1]:
+            for index, (child_config, _) in enumerate(mapping[1:]):
+                for parent_config, _ in mapping[: index + 1]:
                     with self.subTest(
                         msg="Testing if {} is child of {}".format(child_config.__name__, parent_config.__name__)
                     ):
                         self.assertFalse(issubclass(child_config, parent_config))
 
-                        # Check for Slow tokenizer implementation if provided
-                        if child_model_py and parent_model_py:
-                            self.assertFalse(issubclass(child_model_py, parent_model_py))
-
-                        # Check for Fast tokenizer implementation if provided
-                        if child_model_fast and parent_model_fast:
-                            self.assertFalse(issubclass(child_model_fast, parent_model_fast))
-
     @require_tokenizers
     def test_from_pretrained_use_fast_toggle(self):
         self.assertIsInstance(AutoTokenizer.from_pretrained("bert-base-cased", use_fast=False), BertTokenizer)