docs: def saveXml(self, xml):
          """
          Saves the data for this tree to the inputed xml entry.
          
          :param      xml | <xml.etree.ElementTree.Element>
          
          :return     <bool> success
          """
          if xml is None:
              return False
          
          # save order data
          xml.set('headerState', str(self.header().saveState().toBase64()))
          xml.set('sortColumn', str(self.sortColumn()))
          xml.set('sortOrder', str(int(self.sortOrder())))
          xml.set('sortingEnabled', str(self.isSortingEnabled()))
          
          return True