code: function(node, circle, settings) {
        var prefix = settings('prefix') || '';
  
        // Applying changes
        // TODO: optimize - check if necessary
        circle.setAttributeNS(null, 'cx', node[prefix + 'x']);
        circle.setAttributeNS(null, 'cy', node[prefix + 'y']);
        circle.setAttributeNS(null, 'r', node[prefix + 'size']);
  
        // Updating only if not freestyle
        if (!settings('freeStyle'))
          circle.setAttributeNS(
            null, 'fill', node.color || settings('defaultNodeColor'));
  
        // Showing
        circle.style.display = '';
  
        return this;
      }
docs: SVG Element update.
  
  @param  {object}                   node     The node object.
  @param  {DOMElement}               circle   The node DOM element.
  @param  {configurable}             settings The settings function.