[Python] MyPy says 'Incompatible types in assignment' when assigning from multiple inheritance

Here is a sample:

class A: pass

class B: pass

class X(A, B): pass

class Y(A, B): pass

z: B = Y() if temp else X() # MyPy error


The error is Incompatible types in assignment (expression has type "A", variable has type "B").

I could write my method like this:

def func(temp: bool):
x: B = X()
y: B = Y()
w: B = x if temp else y


But is there a better solution?

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