code: function(data) {
          var keyMap = this.options.keyMap;
          return $.map(data, function(value) {
              return {
                  id: value[keyMap.id],
                  title: value[keyMap.title],
                  chosen: !!value[keyMap.chosen]
              };
          });
      }
docs: 预处理左侧数据
  @param {Array} data 源数据
  @return {Array}
  @private