Cleanest way to override __init__ where an optional kwarg must be used after the super() call?

overwrite_init_method.py

#http://stackoverflow.com/questions/5031711/python-cleanest-way-to-override-init-where-an-optional-kwarg-must-be-used
def __init__(self, *args, **kwargs):
    user = kwargs.pop('user', None)
    super(BaseCheckoutForm, self).__init__(*args, **kwargs)
    if user is not None:
        self.prefill_from_user(user)