code: function(args) {
  
                  var tpl = 'SVGFEDropShadowElement' in window
                      ? '<filter><feDropShadow stdDeviation="${blur}" dx="${dx}" dy="${dy}" flood-color="${color}" flood-opacity="${opacity}"/></filter>'
                      : '<filter><feGaussianBlur in="SourceAlpha" stdDeviation="${blur}"/><feOffset dx="${dx}" dy="${dy}" result="offsetblur"/><feFlood flood-color="${color}"/><feComposite in2="offsetblur" operator="in"/><feComponentTransfer><feFuncA type="linear" slope="${opacity}"/></feComponentTransfer><feMerge><feMergeNode/><feMergeNode in="SourceGraphic"/></feMerge></filter>';
  
                  return joint.util.template(tpl)({
                      dx: args.dx || 0,
                      dy: args.dy || 0,
                      opacity: Number.isFinite(args.opacity) ? args.opacity : 1,
                      color: args.color || 'black',
                      blur: Number.isFinite(args.blur) ? args.blur : 4
                  });
              }
docs: `dx` ... horizontal shift (0) `dy` ... vertical shift (0) `blur` ... blur (4) `color` ... color ('black') `opacity` ... opacity (1)