Specify loader for yaml loading.

PiperOrigin-RevId: 330119437

official/modeling/hyperparams/base_config.py

@@ -227,7 +227,7 @@ class Config(params_dict.ParamsDict):
   def from_yaml(cls, file_path: str):
     # Note: This only works if the Config has all default values.
     with tf.io.gfile.GFile(file_path, 'r') as f:
-      loaded = yaml.load(f)
+      loaded = yaml.load(f, Loader=yaml.FullLoader)
       config = cls()
       config.override(loaded)
       return config

official/modeling/hyperparams/params_dict.py

@@ -317,7 +317,7 @@ class ParamsDict(object):
 def read_yaml_to_params_dict(file_path):
   """Reads a YAML file to a ParamsDict."""
   with tf.io.gfile.GFile(file_path, 'r') as f:
-    params_dict = yaml.load(f)
+    params_dict = yaml.load(f, Loader=yaml.FullLoader)
     return ParamsDict(params_dict)
 
 
@@ -438,12 +438,12 @@ def override_params_dict(params, dict_or_string_or_yaml_file, is_strict):
           nested_csv_str_to_json_str(dict_or_string_or_yaml_file))
     except ValueError:
       pass
-    params_dict = yaml.load(dict_or_string_or_yaml_file)
+    params_dict = yaml.load(dict_or_string_or_yaml_file, Loader=yaml.FullLoader)
     if isinstance(params_dict, dict):
       params.override(params_dict, is_strict)
     else:
       with tf.io.gfile.GFile(dict_or_string_or_yaml_file) as f:
-        params.override(yaml.load(f), is_strict)
+        params.override(yaml.load(f, Loader=yaml.FullLoader), is_strict)
   else:
     raise ValueError('Unknown input type to parse.')
   return params