code: def _called_thru_default_qs(self, node):
          
          last_child = node.last_child()
          if not last_child:
              return False
  
          # the default qs manager is called 'objects', we check for it here
          attrname = getattr(last_child, 'attrname', None)
          if attrname != 'objects':
              return False
  
          base_cls = last_child.last_child()
          base_classes = DOCUMENT_BASES
          for cls in base_cls.inferred():
              if node_is_subclass(cls, *base_classes):
                  return True
  
          return False
docs: Checks if an attribute is being accessed throught the default
          queryset manager, ie: MyClass.objects.filter(some='value')