docs: def _preloading_env(self):
          """
          A "stripped" jinja environment.
          """
          ctx = self.env.globals
          try:
              ctx['random_model'] = lambda *a, **kw: None
              ctx['random_models'] = lambda *a, **kw: None
              yield self.env
          finally:
              ctx['random_model'] = jinja2.contextfunction(random_model)
              ctx['random_models'] = jinja2.contextfunction(random_models)