code: function() {
              var $this = $(this);
              var cell = $this.find('td').get($this.treegrid('getSetting', 'treeColumn'));
              var tpl = $this.treegrid('getSetting', 'expanderTemplate');
              var expander = $this.treegrid('getSetting', 'getExpander').apply(this);
              if (expander) {
                  expander.remove();
              }
              $(tpl).prependTo(cell).click(function() {
                  $($(this).closest('tr')).treegrid('toggle');
              });
              return $this;
          }
docs: Initialize expander for node
  
  @returns {Node}