def contact(self, sponsor):
        # comma-separated emails in mailto: should work: https://www.ietf.org/rfc/rfc2368.txt
        # but the commas need to be URL-quoted
        return format_html(
            u'<a href="mailto:{}">{}</a>',
            quote(u','.join(sponsor.contact_emails)),
            sponsor.contact_name
        )