def lessThan(self, leftIndex, rightIndex):
        """ 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.
        """
        leftData  = self.sourceModel().data(leftIndex,  RegistryTableModel.SORT_ROLE)
        rightData = self.sourceModel().data(rightIndex, RegistryTableModel.SORT_ROLE)

        return leftData < rightData
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.