add save_pretrained

pytorch_transformers/modeling_tf_utils.py

@@ -125,7 +125,15 @@ class TFPreTrainedModel(tf.keras.Model):
         """ Save a model and its configuration file to a directory, so that it
             can be re-loaded using the `:func:`~pytorch_transformers.PreTrainedModel.from_pretrained`` class method.
         """
-        raise NotImplementedError
+        assert os.path.isdir(save_directory), "Saving path should be a directory where the model and configuration can be saved"
+
+        # Save configuration file
+        self.config.save_pretrained(save_directory)
+
+        # If we save using the predefined names, we can load using `from_pretrained`
+        output_model_file = os.path.join(save_directory, TF2_WEIGHTS_NAME)
+
+        self.save_weights(output_model_file)
 
     @classmethod
     def from_pretrained(cls, pretrained_model_name_or_path, *model_args, **kwargs):