[Python] Type hint for attribute that might not exist

How do I do a type hint for attribute that might not exist on the object in Python?

For example:

class X:
__slots__ = ('attr',)
attr: int # either int or doesn't exist - what do I put here?


So, concretely:

>>> x = X()
>>> x.attr
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'X' object has no attribute 'attr'
>>> x.attr = 1
>>> x.attr
1


...but there are also cases where __slots__ isn't involved.

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