code: def ensure_backrefs(obj, fields=None):
      
      for ref in _collect_refs(obj, fields):
          updated = ref['value']._update_backref(
              ref['field_instance']._backref_field_name,
              obj,
              ref['field_name'],
          )
          if updated:
              logging.debug('Updated reference {}:{}:{}:{}:{}'.format(
                  obj._name, obj._primary_key, ref['field_name'],
                  ref['value']._name, ref['value']._primary_key,
              ))
docs: Ensure that all forward references on the provided object have the
      appropriate backreferences.
  
      :param StoredObject obj: Database record
      :param list fields: Optional list of field names to check