epub_file = models.FileField(_('EPUB file'), upload_to=book_upload_path('epub'), blank=True)
txt_file = models.FileField(_('TXT file'), upload_to=book_upload_path('txt'), blank=True)
# other files
- medias = models.ManyToManyField(BookMedia)
+ medias = models.ManyToManyField(BookMedia, blank=True)
parent = models.ForeignKey('self', blank=True, null=True, related_name='children')
objects = models.Manager()