add special tokens to pretrain configs of respective lm head models

tests/test_modeling_xlnet.py

@@ -513,14 +513,8 @@ class XLNetModelTest(ModelTesterMixin, unittest.TestCase):
             self.assertIsNotNone(model)
 
 
-def prepare_generation_special_tokens():
-    return {"bos_token_id": 1, "pad_token_id": 5, "eos_token_id": 2}
-
-
 class XLNetModelLanguageGenerationTest(unittest.TestCase):
 
-    special_tokens = prepare_generation_special_tokens()
-
     @slow
     def test_lm_generate_xlnet_base_cased(self):
         model = XLNetLMHeadModel.from_pretrained("xlnet-base-cased")
@@ -917,12 +911,6 @@ class XLNetModelLanguageGenerationTest(unittest.TestCase):
         #  Since, however, he has had difficulty walking with Maria
 
         torch.manual_seed(0)
-        output_ids = model.generate(
-            input_ids,
-            bos_token_id=self.special_tokens["bos_token_id"],
-            pad_token_id=self.special_tokens["pad_token_id"],
-            eos_token_ids=self.special_tokens["eos_token_id"],
-            max_length=200,
-        )
+        output_ids = model.generate(input_ids, max_length=200)
 
         self.assertListEqual(output_ids[0].tolist(), expected_output_ids)