code: function hasCallback (callbackContext = null) {
          if (!this.state[ACTION]
              || callbackContext === this.state[CONTEXT]
              || !this.isText()) {
  
              return false;
          }
          return true;
      }
docs: Returns true, when callback has been prevously set.
  It's usefull, when you don't want to bouce back the methods.
  
  @param {string} [callbackContext]
  @returns {boolean}
  @alias module:callbackMiddleware
  @deprecated - use res.runBookmark()
  @example
  bot.use(['fooRoute', /^foo$/], (req, res) => {
  // set callback, only when this request does not have one
  if (!req.hasCallback()) {
  res.setCallback('fooRoute');
  }
  });