Python未知数据类型强制转换为自定义类类型

class TestPoDr:
    def __init__(self, a: str, b:str):
        self.a = a
        self.b = b

def poi(lu_list: []):
    for h in range(0, 3):
        # 强制类型转换
        test_po_dr: TestPoDr = lu_list[h]
        print(test_po_dr.b)

if __name__ == '__main__':
    list = []
    for i in range(0, 3):
        list.append(TestPoDr(str(i), str(i+1)))