code: def _render_item(self, dstack, key, value = None, **settings):
          
          cur_depth = len(dstack) - 1
  
          treeptrn = ''
          s = self._es_text(settings, settings[self.SETTING_TREE_FORMATING])
          for ds in dstack:
              treeptrn += ' ' + self.fmt_text(self.tchar(settings[self.SETTING_TREE_STYLE], cur_depth, *ds), **s) + ''
  
          strptrn = "{}"
          if value is not None:
              strptrn += ": {}"
          s = self._es_text(settings, settings[self.SETTING_TEXT_FORMATING])
          strptrn = self.fmt_text(strptrn.format(key, value), **s)
  
          return '{} {}'.format(treeptrn, strptrn)
docs: Format single tree line.