add special tokens to pretrain configs of respective lm head models

tests/test_modeling_gpt2.py

@@ -263,14 +263,8 @@ class GPT2ModelTest(ModelTesterMixin, unittest.TestCase):
             self.assertIsNotNone(model)
 
 
-def prepare_generation_special_tokens():
-    return {"bos_token_id": 50256, "eos_token_id": 50256}
-
-
 class GPT2ModelLanguageGenerationTest(unittest.TestCase):
 
-    special_tokens = prepare_generation_special_tokens()
-
     @slow
     def test_lm_generate_gpt2(self):
         model = GPT2LMHeadModel.from_pretrained("gpt2")
@@ -299,11 +293,7 @@ class GPT2ModelLanguageGenerationTest(unittest.TestCase):
         ]  # The dog is cute too. It likes to rub on me and is good for me (the dog
         torch.manual_seed(0)
 
-        output_ids = model.generate(
-            input_ids,
-            bos_token_id=self.special_tokens["bos_token_id"],
-            eos_token_ids=self.special_tokens["eos_token_id"],
-        )
+        output_ids = model.generate(input_ids)
 
         self.assertListEqual(output_ids[0].tolist(), expected_output_ids)
 
@@ -335,10 +325,5 @@ class GPT2ModelLanguageGenerationTest(unittest.TestCase):
         ]  # The dog is cute though he can sometimes just walk in the park. It is not very nice to
         torch.manual_seed(0)
 
-        output_ids = model.generate(
-            input_ids,
-            bos_token_id=self.special_tokens["bos_token_id"],
-            eos_token_ids=self.special_tokens["eos_token_id"],
-        )
-
+        output_ids = model.generate(input_ids)
         self.assertListEqual(output_ids[0].tolist(), expected_output_ids)