How to use the sigal.signals.gallery_build function in sigal

def register(settings):
    signals.gallery_build.connect(generate_feeds)

def register(settings):
    signals.gallery_build.connect(generate_media_pages)

file=self.progressbar_target) as albums:
                for album in albums:
                    if album.albums:
                        if album.medias:
                            self.logger.warning(
                                "Album %s contains sub-albums and images. "
                                "Please move images to their own sub-album. "
                                "Images in album %s will not be visible.",
                                album.title, album.title
                            )
                        album_list_writer.write(album)
                    else:
                        album_writer.write(album)
        print('')

        signals.gallery_build.send(self)

def register(settings):
    if settings.get('upload_s3_options'):
        signals.gallery_build.connect(upload_s3)
    else:
        logger.warning('Upload to S3 is not configured.')

def register(settings):
    signals.gallery_build.connect(save_cache)
    signals.album_initialized.connect(load_exif)

def register(settings):
    if settings['write_html']:
        signals.gallery_build.connect(compress_gallery)