Return a new `p:bgPr` element with noFill properties.

def add_noFill_bgPr(self):
        """Return a new `p:bgPr` element with noFill properties."""
        xml = (
            '<p:bgPr %s>\n'
            '  <a:noFill/>\n'
            '  <a:effectLst/>\n'
            '</p:bgPr>' % nsdecls('a', 'p')
        )
        bgPr = parse_xml(xml)
        self._insert_bgPr(bgPr)
        return bgPr