def METHOD_NAME(enumeration: Enumeration) -> typing.Optional[str]:
    fields = enumeration.secondary_fields
    if not fields:
        return None
    header = '\n\n<p>The following fields also use these values:</p>\n<ul>\n'
    items = ''.join('  <li>{}({})</li>\n'.format(field.name, field.tag) for field in fields)
    footer = '</ul>\n'
    return '{}{}{}'.format(header, items, footer)