Format single list item.

def _render_item(self, depth, key, value = None, **settings):
        """
        Format single list item.
        """
        strptrn  = self.INDENT * depth

        lchar = self.lchar(settings[self.SETTING_LIST_STYLE])
        s = self._es_text(settings, settings[self.SETTING_LIST_FORMATING])
        lchar = self.fmt_text(lchar, **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(self.INDENT * depth, lchar, strptrn)