def __init__(self, min_value, max_value, step, instance=None,
        can_delete_vote=True, key='', read_only=False, default='',
        template='ratings/slider_widget.html', attrs=None):
        """
        The argument *default* is used when the initial value is None.
        """
        super(SliderWidget, self).__init__(attrs)
        self.min_value = min_value
        self.max_value = max_value
        self.step = step
        self.instance = instance
        self.can_delete_vote = can_delete_vote
        self.read_only = read_only
        self.default = default
        self.template = template
        self.key = key