code: function SetCache(values) {
          var index = -1,
              length = values == null ? 0 : values.length;
  
          this.__data__ = new MapCache();
          while (++index < length) {
              this.add(values[index]);
          }
      }
docs: /*------------------------------------------------------------------------ 
  
  Creates an array cache object to store unique values.
  
  @private
  @constructor
  @param {Array} [values] The values to cache.