An unused argument can lead to confusions. It should be removed. If this variable is necessary, name the variable _ or start the name with unused or _unused.

Bad practice

def square(x, y=1):
    return x * x

class MySubClass(MyClass):
    def __init__(self, number):
        self.value = 42  # argument `number` remains unused

Preferred:

def square(x):
    return x * x

class MySubClass(MyClass):
    def __init__(self, _):
        self.value = 42