code: function(delta) {
          return new $.Rect(
              this.x + delta.x,
              this.y + delta.y,
              this.width,
              this.height,
              this.degrees);
      }
docs: Translate/move this Rect by a vector and return new Rect.
  @function
  @param {OpenSeadragon.Point} delta The translation vector.
  @returns {OpenSeadragon.Rect} A new rect with altered position