code: def _is_custom_qs_manager(funcdef):
      
  
      decors = getattr(funcdef, 'decorators', None)
      if decors:
          for dec in decors.get_children():
              try:
                  if dec.name == 'queryset_manager':  # pragma no branch
                      return True
              except AttributeError:
                  continue
  
      return False
docs: Checks if a function definition is a queryset manager created
      with the @queryset_manager decorator.