code: function(args) {
  
                  var x = Number.isFinite(args.x) ? args.x : 2;
  
                  return joint.util.template('<filter><feGaussianBlur stdDeviation="${stdDeviation}"/></filter>')({
                      stdDeviation: Number.isFinite(args.y) ? [x, args.y] : x
                  });
              }
docs: `x` ... horizontal blur (2) `y` ... vertical blur (optional)