'List subtitles.
:param video: video to list subtitles for.
:type video: :class:`~subliminal.video.Video`
:param languages: languages to search for.
:type languages: set of :class:`~babelfish.language.Language`
:return: found subtitles.
:rtype: list of :class:`~subliminal.subtitle.Subtitle`'

def list_subtitles(self, video, languages):

    subtitles = []
    for name in self.providers:
        if (name in self.discarded_providers):
            logger.debug('Skipping    discarded    provider    %r', name)
            continue
        provider_subtitles = self.list_subtitles_provider(name, video, languages)
        if (provider_subtitles is None):
            logger.info('Discarding    provider    %s', name)
            self.discarded_providers.add(name)
            continue
        subtitles.extend(provider_subtitles)
    return subtitles
