code: function (aggId) {
      if (!aggId || !_.isString(aggId)) {
        var err = new Error('Please pass a valid aggregate id!');
        debug(err);
        throw err;
      }
  
      if (this.queue[aggId] && this.queue[aggId].length > 0) {
        var nextCmd = this.queue[aggId][0];
        return nextCmd;
      }
  
      return null;
    }
docs: Returns next command in the queue
  @param {String} aggId The passed aggregate id.
  @returns {Object}