code: def _construct_arrow_tip(self, pos):
          
          arrow_tip = None
          width = 0
          if self._arrow_tip_char:
              txt = urwid.Text(self._arrow_tip_char)
              arrow_tip = urwid.AttrMap(
                  txt, self._arrow_tip_att or self._arrow_att)
              width = len(self._arrow_tip_char)
          return width, arrow_tip
docs: returns arrow tip as (width, widget)