docs: def register_jinja_loaders(self, *loaders):
          """Register one or many `jinja2.Loader` instances for templates lookup.
  
          During application initialization plugins can register a loader so that
          their templates are available to jinja2 renderer.
  
          Order of registration matters: last registered is first looked up (after
          standard Flask lookup in app template folder). This allows a plugin to
          override templates provided by others, or by base application. The
          application can override any template from any plugins from its template
          folder (See `Flask.Application.template_folder`).
  
          :raise: `ValueError` if a template has already been rendered
          """
          if not hasattr(self, "_jinja_loaders"):
              raise ValueError(
                  "Cannot register new jinja loaders after first template rendered"
              )
  
          self._jinja_loaders.extend(loaders)