code: def lessThan(self, leftIndex, rightIndex):
          
          leftData  = self.sourceModel().data(leftIndex,  RegistryTableModel.SORT_ROLE)
          rightData = self.sourceModel().data(rightIndex, RegistryTableModel.SORT_ROLE)
  
          return leftData < rightData
docs: Returns true if the value of the item referred to by the given index left is less than
              the value of the item referred to by the given index right, otherwise returns false.