docs: def exportTreeItem(self, sheet, cols, item):
          """
          Exports the inputed item to the given Excel worksheet for the
          given visible columns.
          
          :param      sheet | <xlwt.WorkSheet>
                      cols  | [<int>, ..]
                      item  | <QTreeWidgetItem>
          """
          # export item information
          for c, col in enumerate(cols):
              data = unwrapVariant(item.data(Qt.EditRole, col))
              if data:
                  sheet.write(self._currrow, c, nativestring(data))
              else:
                  sheet.write(self._currrow, c, nativestring(item.text(col)))
          
          self._currrow += 1
          
          # export children as rows
          for c in range(item.childCount()):
              self.exportTreeItem(sheet, cols, item.child(c))