class Creator(object):
    """
    A descriptor that invokes `to_python` when attributes are set.
    This provides backwards compatibility for fields that used to use
    SubfieldBase which will be removed in Django1.10
    """

    def __init__(self, field):
        self.field = field

    def __get__(self, obj, type=None):
        if obj is None:
            return self
        return obj.__dict__[self.field.name]

    def __set__(self, obj, value):
        obj.__dict__[self.field.name] = self.field.to_python(value)