def METHOD_NAME(self):
    cleaned_data = super().METHOD_NAME()
    apt_number = cleaned_data.get("apt_number")
    no_apt_number = cleaned_data.get("no_apt_number")
    if apt_number and no_apt_number:
        raise ValidationError(
            _(
                "Please either provide an apartment number or check the "
                '"I have no apartment number" checkbox (but not both).'
            )
        )
    if not apt_number and not no_apt_number:
        raise ValidationError(
            _(
                "Please either provide an apartment number or check the "
                '"I have no apartment number" checkbox.'
            )
        )
    if "no_apt_number" in cleaned_data:
        cleaned_data.pop("no_apt_number")
    return cleaned_data