code: function (fn, args) {
        fn = fn.toUpperCase();
        args = args || [];
  
        if (instance.helper.SUPPORTED_FORMULAS.indexOf(fn) > -1) {
          if (instance.formulas[fn]) {
            return instance.formulas[fn].apply(this, args);
          }
        }
  
        throw Error('NAME');
      }
docs: call function from formula
  @param {String} fn
  @param {Array} args
  @returns {*}