code: def is_changed(obj):
      
      revision_field = get_version_fieldname(obj)
      version = get_revision_of_object(obj)
      return not obj.__class__.objects.filter(**{obj._meta.pk.name: obj.pk,
                                                 revision_field: version}).exists()
docs: returns True if `obj` is changed or deleted on the database
      :param obj:
      :return: