How to: Override inherited mutable static variables in python

class MyClass(SomeParentClass):
    default_messages = {'msg': 'this is default message'}
    
    def __init__(self):
        messages = {}
        for c in reversed(self.__class__.__mro__):
            messages.update(getattr(c, 'default_error_messages', {}))
        messages.update(error_messages or {})