[Python] Propagate assertion type check to caller

I want to assert the type of an object in a function without having to return it, but I can't find how to do it.

For example:

from typing import Optional, TypeVar

T = TypeVar('T')

def assert_non_null(_object: Optional[T]):
assert _object is not None

def f(a: Optional[float]):
assert_non_null(a)
b: float = a # error because "a" can be null


Whereas this works (but its not what I'm looking for):

from typing import Optional, TypeVar

T = TypeVar('T')

def extract_non_null(_object: Optional[T]):
assert _object is not None
return _object

def g(a: Optional[float]):
a = extract_non_null(a)
b: float = a # its fine because the function returns the type T (float)


Is there a way to add type annotation on side effects to make sure calling assert_non_null has the same effect as calling assert is not None directly?

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