TF: standardize `test_model_common_attributes` for language models (#23457)

tests/test_modeling_tf_common.py

@@ -1013,7 +1013,7 @@ class TFModelTesterMixin:
             check_hidden_states_output(config, inputs_dict, model_class)
 
     def test_model_common_attributes(self):
-        config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()
+        config, _ = self.model_tester.prepare_config_and_inputs_for_common()
         text_in_text_out_models = (
             get_values(TF_MODEL_FOR_CAUSAL_LM_MAPPING)
             + get_values(TF_MODEL_FOR_MASKED_LM_MAPPING)
@@ -1023,24 +1023,27 @@ class TFModelTesterMixin:
 
         for model_class in self.all_model_classes:
             model = model_class(config)
-            assert isinstance(model.get_input_embeddings(), tf.keras.layers.Layer)
-            if model_class in text_in_text_out_models:
-                x = model.get_output_embeddings()
-                assert isinstance(x, tf.keras.layers.Layer)
-                name = model.get_bias()
-                assert isinstance(name, dict)
-                for k, v in name.items():
-                    assert isinstance(v, tf.Variable)
+            self.assertIsInstance(model.get_input_embeddings(), tf.keras.layers.Layer)
+
+            legacy_text_in_text_out = model.get_lm_head() is not None
+            if model_class in text_in_text_out_models or legacy_text_in_text_out:
+                out_embeddings = model.get_output_embeddings()
+                self.assertIsInstance(out_embeddings, tf.keras.layers.Layer)
+                bias = model.get_bias()
+                if bias is not None:
+                    self.assertIsInstance(bias, dict)
+                    for _, v in bias.items():
+                        self.assertIsInstance(v, tf.Variable)
             elif model_class in speech_in_text_out_models:
-                x = model.get_output_embeddings()
-                assert isinstance(x, tf.keras.layers.Layer)
-                name = model.get_bias()
-                assert name is None
+                out_embeddings = model.get_output_embeddings()
+                self.assertIsInstance(out_embeddings, tf.keras.layers.Layer)
+                bias = model.get_bias()
+                self.assertIsNone(bias)
             else:
-                x = model.get_output_embeddings()
-                assert x is None
-                name = model.get_bias()
-                assert name is None
+                out_embeddings = model.get_output_embeddings()
+                assert out_embeddings is None
+                bias = model.get_bias()
+                self.assertIsNone(bias)
 
     def test_determinism(self):
         config, inputs_dict = self.model_tester.prepare_config_and_inputs_for_common()