code: def sortData( self, column ):
          
          value = unwrapVariant(self.data(column, self.SortRole))
          if value is None:
              return None
          return unwrapVariant(self.data(column, QtCore.Qt.EditRole))
docs: Returns the data to be used when sorting.  If no sort data has been
          explicitly defined, then the value in the EditRole for this item's
          column will be used.
          
          :param      column | <int>
          
          :return     <variant>