Python3.x 使用正确的数据类型时，使用 Cerberus 验证 JSON 架构会引发错误

我正在try 验证JSON模式.为released Cerberus指定正确的数据类型date时，会抛出一个错误.

def test_validate_books_schema():
    schema = {
            "url" : {'type': 'string'},
            "name" : {'type': 'string'},
            "isbn" : {'type': 'string'},
            "authors" : {'type': ['string','list']},
            "numberOfPages" : {'type': 'integer'},
            "publisher" : {'type': 'string'},
            "country" : {'type': 'string'},
            "mediaType" : {'type': 'string'},
            "released" : {'type': 'date'},
            "characters" : {'type': ['string','list']},
            "povCharacters" : {'type': ['string','list']}            
        }

    response = requests.get("https://www.anapioficeandfire.com/api/books/1")
    
    v = Validator(schema)
    validate_response = v.validate(response.json())
    assert_that(validate_response, description=v.errors).is_true()

./tests/books/test_books.py::test_validate_books_schema Failed: [undefined]AssertionError: [{'released': ['must be of date type']}] Expected <True>, but was not.
def test_validate_books_schema():
        schema = {
                "url" : {'type': 'string'},
                "name" : {'type': 'string'},
                "isbn" : {'type': 'string'},
                "authors" : {'type': ['string','list']},
                "numberOfPages" : {'type': 'integer'},
                "publisher" : {'type': 'string'},
                "country" : {'type': 'string'},
                "mediaType" : {'type': 'string'},
                "released" : {'type': 'date'},
                "characters" : {'type': ['string','list']},
                "povCharacters" : {'type': ['string','list']}
            }
    
        response = requests.get("https://www.anapioficeandfire.com/api/books/1")
    
        v = Validator(schema)
        validate_response = v.validate(response.json())
>       assert_that(validate_response, description=v.errors).is_true()
E       AssertionError: [{'released': ['must be of date type']}] Expected <True>, but was not.

tests\books\test_books.py:42: AssertionError

documentation表示released的数据类型是Date.当我为released指定string时，它是有效的.