docs: function() {
          if (this.length === 1 && !this.__frozen) {
              this.trigger("Freeze", this);
              this._freezeCallbacks();
              this.__frozen = true;
          } else {
              for (var i = 0; i < this.length; i++) {
                  var e = entities[this[i]];
                  if (e && !e.__frozen) {
                      e.trigger("Freeze", e);
                      e._freezeCallbacks();
                      // Set a frozen flag.  (This is distinct from the __callbackFrozen flag)
                      e.__frozen = true;
                  }
              }
          }
          return this;
      }