docs: function (mapName, object) {
              var mapFunction = this.mapFunctions[mapName],
                  index,
                  value,
                  emit = function (idx, val) {
                      index = idx;
                      value = val;
                  };
  
              mapFunction.call(object, object, emit);
  
              if (this.maps[mapName][index] === undefined) {
                  this.maps[mapName][index] = [];
              }
              this.maps[mapName][index].push(value);
              this.mapValues[object.id][mapName] = index;
              return this;
          }