Pass kwargs to configuration (#3147)

* Pass kwargs to configuration

* Setter

* test

src/transformers/configuration_utils.py

@@ -98,6 +98,18 @@ class PretrainedConfig(object):
                 logger.error("Can't set {} with value {} for {}".format(key, value, self))
                 raise err
 
+    @property
+    def num_labels(self):
+        return self._num_labels
+
+    @num_labels.setter
+    def num_labels(self, num_labels):
+        self._num_labels = num_labels
+        self.id2label = {i: "LABEL_{}".format(i) for i in range(self.num_labels)}
+        self.id2label = dict((int(key), value) for key, value in self.id2label.items())
+        self.label2id = dict(zip(self.id2label.values(), self.id2label.keys()))
+        self.label2id = dict((key, int(value)) for key, value in self.label2id.items())
+
     def save_pretrained(self, save_directory):
         """
         Save a configuration object to the directory `save_directory`, so that it

tests/test_configuration_common.py

@@ -57,8 +57,18 @@ class ConfigTester(object):
 
         self.parent.assertEqual(config_second.to_dict(), config_first.to_dict())
 
+    def create_and_test_config_with_num_labels(self):
+        config = self.config_class(**self.inputs_dict, num_labels=5)
+        self.parent.assertEqual(len(config.id2label), 5)
+        self.parent.assertEqual(len(config.label2id), 5)
+
+        config.num_labels = 3
+        self.parent.assertEqual(len(config.id2label), 3)
+        self.parent.assertEqual(len(config.label2id), 3)
+
     def run_common_tests(self):
         self.create_and_test_config_common_properties()
         self.create_and_test_config_to_json_string()
         self.create_and_test_config_to_json_file()
         self.create_and_test_config_from_and_save_pretrained()
+        self.create_and_test_config_with_num_labels()