def get_widget_or_404(self):
        """
        Get and return widget from cache.

        Raises:
            Http404: If if the widget can not be found or no id is provided.

        Returns:
            ModelSelect2Mixin: Widget from cache.

        """
        field_id = self.kwargs.get('field_id', self.request.GET.get('field_id', None))
        if not field_id:
            raise Http404('No "field_id" provided.')
        try:
            key = signing.loads(field_id)
        except BadSignature:
            raise Http404('Invalid "field_id".')
        else:
            cache_key = '%s%s' % (settings.SELECT2_CACHE_PREFIX, key)
            widget_dict = cache.get(cache_key)
            if widget_dict is None:
                raise Http404('field_id not found')
            if widget_dict.pop('url') != self.request.path:
                raise Http404('field_id was issued for the view.')
        qs, qs.query = widget_dict.pop('queryset')
        self.queryset = qs.all()
        widget_dict['queryset'] = self.queryset
        widget_cls = widget_dict.pop('cls')
        return widget_cls(**widget_dict)
Get and return widget from cache.

        Raises:
            Http404: If if the widget can not be found or no id is provided.

        Returns:
            ModelSelect2Mixin: Widget from cache.