code: def query_delete(cls, expression=None):
          
          if expression is not None:
              executor = Executor(cls.__database__)
              result = executor.execute(expression)
          else:
              result = cls._query.all_index()
  
          for hash_id in result:
              cls.load(hash_id, convert_key=False).delete()
docs: Delete model instances matching the given expression (if
          specified). If no expression is provided, then all model instances
          will be deleted.
  
          :param expression: A boolean expression to filter by.