code: function (item, value) {
          var match,
              val,
              i;
  
          match = _.isString(item) ?
              this.reference[this._postman_listIndexCaseInsensitive ? item.toLowerCase() : item] :
              this.filter(function (member) {
                  return member === item;
              });
  
          // If we don't have a match, there's nothing to do
          if (!match) { return false; }
  
          // if no value is provided, just check if item exists
          if (arguments.length === 1) {
              return Boolean(_.isArray(match) ? match.length : match);
          }
  
          // If this property allows multiple values and we get an array, we need to iterate through it and see
          // if any element matches.
          if (this._postman_listAllowsMultipleValues && _.isArray(match)) {
              for (i = 0; i < match.length; i++) {
  
                  // use the value of the current element
                  val = _.isFunction(match[i].valueOf) ? match[i].valueOf() : match[i];
  
                  if (val === value) { return true; }
              }
  
              // no matches were found, so return false here.
              return false;
          }
  
          // We didn't have an array, so just check if the matched value equals the provided value.
          _.isFunction(match.valueOf) && (match = match.valueOf());
  
          return match === value;
      }
docs: Check whether an item exists in this list
  
  @param {String|PropertyList.Type} item
  @param {*=} value
  @returns {Boolean}