Standard rendering of bar graph.

def _render(self):
        ''' Standard rendering of bar graph. '''
        cm_chars = self._comp_style(self.icons[_ic] * self._num_complete_chars)
        em_chars = self._empt_style(self.icons[_ie] * self._num_empty_chars)
        return f'{self._first}{cm_chars}{em_chars}{self._last} {self._lbl}'