code: def get_backend_path(service):
      
      for backend in _get_backends():
          try:
              if backend.service_allowed(service):
                  return "%s.%s" % (backend.__class__.__module__, backend.__class__.__name__)
          except AttributeError:
              raise NotImplementedError("%s.%s.service_allowed() not implemented" % (
                  backend.__class__.__module__, backend.__class__.__name__)
              )
      return None
docs: Return the dotted path of the matching backend.