class AttributeGetter:
    mandatory = []

    # noinspection PyUnusedLocal
    def __init__(self, *args, **kwargs):
        if not hasattr(self, 'value'):
            self.value = None

        for m in self.mandatory:
            if not hasattr(self, m) or getattr(self, m) is None:
                raise ValueError(f'Value attribute must have {m} assigned')

    def get_value(self):
        return self.value

    def get_value_serialized(self):
        return self.value