code: func toJSONPb(_ *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
  	var msg *Message
  	var emitDefaults starlark.Bool
  	if err := starlark.UnpackArgs("to_jsonpb", args, kwargs, "msg", &msg, "emit_defaults?", &emitDefaults); err != nil {
  		return nil, err
  	}
  	pb, err := msg.ToProto()
  	if err != nil {
  		return nil, err
  	}
  	// More jsonpb Marshaler options may be added here as needed.
  	var jsonMarshaler = &jsonpb.Marshaler{Indent: "\t", EmitDefaults: bool(emitDefaults)}
  	str, err := jsonMarshaler.MarshalToString(pb)
  	if err != nil {
  		return nil, err
  	}
  	return starlark.String(str), nil
  }
docs: // toJSONPb takes a single protobuf message and serializes it using JSONPB
  // serialization.