code: func NewRPCErrorResponse(id string, code int, message string) RPCResponse {
  	return RPCResponse(&RPCErrorResponse{
  		Error:   &RPCError{code, message},
  		Id:      id,
  		JSONRPC: "2.0",
  	})
  }
docs: // NewRPCErrorResponse creates a new error-response object from the error code and message