python之singledispatch单分派问题

@singledispatch
def inner_as_dict() -> object:
    """
    singledispatch方法，对于不同类型的键，注册不同的序列化为字典的方法
    """
    return None
@inner_as_dict.register
def _(element) -> None
    return None
@inner_as_dict.register(TestData1)
def _(element: List[TestData1]) -> [Dict]:
    result = []
    for i in element:
        tmp = asdict(i)
        tmp_list = [i.msg for i in tmp["code"]]
        tmp["msg"] = tmp_list if tmp_list else ["-"]
        result.append(tmp)
    return result
@inner_as_dict.register(TestData2)
def _(element: TestData2) -> List[Dict]:
    result: List[Dict] = []
    if not element.data:
        for message in element.message.splitlines():
            single_fail_res = {"item": message.split(",")[0], "result": False}
            result.append(single_fail_res)
    return result
@inner_as_dict.register(TestData3)
def _(element: TestData3) -> Tuple[int, str]:
    verify_result = 0 if element.result else -1
    verify_message = element.error.msg if element.error else "-"
    return verify_result, verify_message
@inner_as_dict.register(int)
@inner_as_dict.register(float)
@inner_as_dict.register(bool)
@inner_as_dict.register(str)
@inner_as_dict.register(list)
@inner_as_dict.register(dict)
@inner_as_dict.register(tuple)
def _(element: Union[int, float, bool, str, List, Dict, Tuple]) -> Union[int, float, bool, str, List, Dict, Tuple]:
    return element

from functools import singledispatch
@singledispatch
def add(x, y):
    print("Default implementation for integers")
    return x + y
@add.register(int)
def _(x, y):
    print("Implementation for integers")
    return x + y
@add.register(str)
def _(x, y):
    print("Implementation for strings")
    return x + y
print(add(1, 2)) # Output: Default implementation for integers -> 3
print(add("hello", "world")) # Output: Implementation for strings -> helloworld
print(add(1.5, 2.5)) # Output: Default implementation for integers -> 4
print(add("foo", "bar")) # Output: Default implementation for integers -> foobar