Add a stub for google.protobuf.json_format. (#2479)

third_party/2and3/google/protobuf/json_format.pyi

@@ -0,0 +1,31 @@
+import sys
+from typing import Any, Dict, Text, TypeVar, Union
+from google.protobuf.message import Message
+
+_MessageVar = TypeVar('_MessageVar', bound=Message)
+
+class Error(Exception): ...
+
+class ParseError(Error): ...
+
+class SerializeToJsonError(Error): ...
+
+def MessageToJson(
+    message: Message,
+    including_default_value_fields: bool = ...,
+    preserving_proto_field_name: bool = ...,
+    indent: int = ...,
+    sort_keys: bool = ...,
+    use_integers_for_enums: bool = ...
+) -> str: ...
+
+def MessageToDict(
+    message: Message,
+    including_default_value_fields: bool = ...,
+    preserving_proto_field_name: bool = ...,
+    use_integers_for_enums: bool = ...
+) -> Dict[Text, Any]: ...
+
+def Parse(text: Union[bytes, Text], message: _MessageVar, ignore_unknown_fields: bool = ...) -> _MessageVar: ...
+
+def ParseDict(js_dict: Any, message: _MessageVar, ignore_unknown_fields: bool = ...) -> _MessageVar: ...