code: function()
    {
      this.indices = {};
  
      for (var i = 0, l = this.keys.length; i < l; i++)
      {
        this.indices[ this.keys[ i ] ] = i;
      }
  
      return this;
    }
docs: Rebuilds the index based on the keys.
  
  @return {Rekord.Map} -
  The reference to this map.