[Python] Python typing is rejecting override of a property with a child of its type

Here is an example of my issue:

class Foo:
pass

class FooChild(Foo):
pass

class Bar:
def __init__(self):
self.prop: Foo

class BarChild(Bar):
def __init__(self):
self.prop: FooChild = FooChild()


Here I have a warning on the override of the prop property:

"prop" overrides symbol of same name in class "Bar"
Variable is mutable so its type is invariant
Override type "FooChild" is not the same as base type "Foo"


I am confused as to why this is an error. A child would implement its parent, so why can I not override it in this case?

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