add to_json_file method to configuration classes

tests/modeling_gpt2_test.py

@@ -16,6 +16,7 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
+import os
 import unittest
 import json
 import random
@@ -176,6 +177,14 @@ class GPT2ModelTest(unittest.TestCase):
         self.assertEqual(obj["vocab_size"], 99)
         self.assertEqual(obj["n_embd"], 37)
 
+    def test_config_to_json_file(self):
+        config_first = GPT2Config(vocab_size_or_config_json_file=99, n_embd=37)
+        json_file_path = "/tmp/config.json"
+        config_first.to_json_file(json_file_path)
+        config_second = GPT2Config.from_json_file(json_file_path)
+        os.remove(json_file_path)
+        self.assertEqual(config_second.to_dict(), config_first.to_dict())
+
     def run_tester(self, tester):
         config_and_inputs = tester.prepare_config_and_inputs()
         output_result = tester.create_gpt2_model(*config_and_inputs)