def __init__(self, element_type, default=NULL, required=True, validation=None,
                 in_dump=True, default_in_dump=True, nullable=False, immutable=False, aliases=()):
        self._element_type = element_type
        super(ListField, self).__init__(default, required, validation,
                                        in_dump, default_in_dump, nullable, immutable, aliases)