def METHOD_NAME(self, value: typing.Union[str, T], context: typing.MutableMapping) -> None:
    """Report unknown value."""
    if not value or not self.reportable:
        return
    if 'report' in context:
        report_map = context['report'].setdefault(self.description, {})
        if value not in report_map:
            report_map[value] = context['path']
    logger.info('Invalid %s: %r', self.description, value)