docs: def inject(self, state, response):
          """ Inject Debug Toolbar code to response body. """
          html = yield from self.app.ps.jinja2.render(
              'debugtoolbar/inject.html',
              static_path=self.cfg.prefix + 'static',
              toolbar_url=self.cfg.prefix + state.id,
          )
          html = html.encode(state.request.charset or 'utf-8')
          response.body = RE_BODY.sub(html + b'</body>', response.body)
          return response