code: function(node, settings) {
        var prefix = settings('prefix') || '',
            circle = document.createElementNS(settings('xmlns'), 'circle');
  
        // Defining the node's circle
        circle.setAttributeNS(null, 'data-node-id', node.id);
        circle.setAttributeNS(null, 'class', settings('classPrefix') + '-node');
        circle.setAttributeNS(
          null, 'fill', node.color || settings('defaultNodeColor'));
  
        // Returning the DOM Element
        return circle;
      }
docs: SVG Element creation.
  
  @param  {object}                   node     The node object.
  @param  {configurable}             settings The settings function.