widget.py

class MyWidget(forms.widgets.CheckboxSelectMultiple):
    template_name = 'web_admin/partial/checkbox.html'
    option_template_name = 'web_admin/partial/panel_item_p.html'

    def get_context(self, name, value, attrs):
        ctx = super().get_context(name, value, attrs)
        # update the context adding the qs
        ctx.update(dict(qs=self.qs))
        return ctx