code: function() {
          var me = this,
              header = me.getGroupedHeader();
  
          if (me.hideGroupedHeader && header) {
              Ext.suspendLayouts();
              if (me.prunedHeader && me.prunedHeader !== header) {
                  me.prunedHeader.show();
              }
              me.prunedHeader = header;
              header.hide();
              Ext.resumeLayouts(true);
          }
      }
docs: Prunes the grouped header from the header container
  @private