Everything is mutable in python so just assign types normally. Its built into the language. No need to do anything!
class Poly:
attribute: str
class Mutable(Poly):
def __init__(self):
super().__init__()
self.attribute = "Amazing!"
abra: int = 1
kadabra: str = "alakazam"
abra = kadabra
print(abra)
stdout "alakazam"