code: function(tx, ty, opt) {
  
          // enrich the option object
          opt = opt || {};
          opt.translateBy = opt.translateBy || this.id;
          opt.tx = tx;
          opt.ty = ty;
  
          return this.applyToPoints(function(p) {
              return { x: (p.x || 0) + tx, y: (p.y || 0) + ty };
          }, opt);
      }
docs: Transformations