docs: function(cbr) {
          cbr = cbr || {};
          if (!this._cbr) {
              return this.mbr(cbr);
          } else {
              cbr._x = this._cbr._x;
              cbr._y = this._cbr._y;
              cbr._w = this._cbr._w;
              cbr._h = this._cbr._h;
              return cbr;
          }
      }