code: function callbackWrapper(error, response) {
          self.debug('methodCall->callbackWrapper', error, response);
          // TODO: error should be customized to handle more error types
          if (error /*&& error.code === "ENOTFOUND" && error.syscall === "getaddrinfo"*/) {
            error.message = "Unable to connect to WordPress.";
            return callback.call(self, error);
          }
  
          // Parse Response.
          if (_.isString(response) && self.common.is_numeric(response)) {
            response = parseInt(response);
          }
          callback.call(self, error, response);
        }
docs: Handle RPC Method Callback.
  
  @param {Error} error
  @param {string} response
  @returns {*}