code: function(element) {
      if (element) {
        // ensure the presence of a dom element
        element = typeof element == 'string' ?
          document.getElementById(element) :
          element
  
        // If the target is an svg element, use that element as the main wrapper.
        // This allows svg.js to work with svg documents as well.
        if (element.nodeName == 'svg') {
          this.constructor.call(this, element)
        } else {
          this.constructor.call(this, SVG.create('svg'))
          element.appendChild(this.node)
          this.size('100%', '100%')
        }
  
        // set svg element attributes and ensure defs node
        this.namespace().defs()
      }
    }
docs: Initialize node