def focus_first_reply(self):
        """move focus to first reply to currently focussed message"""
        mid = self.get_selected_mid()
        newpos = self._tree.first_child_position(mid)
        if newpos is not None:
            newpos = self._sanitize_position((newpos,))
            self.body.set_focus(newpos)
move focus to first reply to currently focussed message