A helper to move the chidren of a group.

def _move_group_helper(self, group):
        """A helper to move the chidren of a group."""

        for i in group.children:
            self.groups.remove(i)
            i.level = group.level + 1
            self.groups.insert(self.groups.index(group) + 1, i)
            if i.children:
                self._move_group_helper(i)