code: function ($node, relation) {
        if (!$node || !($node instanceof $) || !$node.is('.node')) {
          return $();
        }
        if (relation === 'parent') {
          return $node.closest('.nodes').parent().children(':first').find('.node');
        } else if (relation === 'children') {
          return $node.closest('tr').siblings('.nodes').children().find('.node:first');
        } else if (relation === 'siblings') {
          return $node.closest('table').parent().siblings().find('.node:first');
        } else {
          return $();
        }
      }
docs: find the related nodes