code: def get_source(
              self, environment: Environment, template: str,
      ) -> Tuple[str, Optional[str], Callable]:
          
          for loader in self._loaders():
              try:
                  return loader.get_source(environment, template)
              except TemplateNotFound:
                  continue
          raise TemplateNotFound(template)
docs: Returns the template source from the environment.
  
          This considers the loaders on the :attr:`app` and blueprints.