old_contents: from django.db import models
  
  # class Library(models.Model):
  #     ...
  
  
  # class BookShelf(models.Model):
  #     name = models.CharField("研究室名", max_length=191)
  
  
  class MyBook(models.Model):
      book_info = models.ForeignKey('BookInfo')
      buy_date = models.DateField("購入日", null=True)
      buy_user = models.CharField("購入希望者", max_length=191, blank=True)
      manager = models.CharField("管理責任者", max_length=191)
      buy_at = models.CharField("購入場所", max_length=191, blank=True)
      purpose = models.TextField("購入目的", blank=True)
      money_source = models.CharField("資金源", max_length=191, blank=True)
      book_expire_at = models.DateField("本の賞味期限", null=True)
      created_at = models.DateTimeField(auto_now_add=True)
      updated_at = models.DateTimeField(auto_now=True)
  
  
  class BookInfo(models.Model):
      isbn = models.CharField("ISBN", primary_key=True, max_length=20)
      title = models.CharField("タイトル", max_length=191)
      title_kana = models.CharField("タイトル(カナ)", max_length=191, blank=True)
      sub_title = models.CharField("サブタイトル", max_length=191, blank=True)
      sub_title_kana = models.CharField("サブタイトル(カナ)", max_length=191, blank=True)
      series_name = models.CharField("シリーズ名", max_length=191, blank=True)
      series_name_kana = models.CharField("シリーズ名(カナ)", max_length=191, blank=True)
      author = models.CharField("著者", max_length=191, blank=True)
      author_kana = models.CharField("著者(カナ)", max_length=191, blank=True)
      publisher_name = models.CharField("出版社", max_length=191, blank=True)
      book_size = models.CharField("本サイズ", max_length=191, blank=True)
      item_caption = models.TextField("キャプション", blank=True)
      sales_date = models.DateField("発売日", null=True)
      item_price = models.IntegerField("価格", blank=True)
      image_url = models.URLField("画像URL", blank=True)
      genre_id = models.CharField("書籍ジャンル", max_length=191, blank=True)
  
new_contents: from django.db import models
  
  # class Library(models.Model):
  #     ...
  
  
  # class BookShelf(models.Model):
  #     name = models.CharField("研究室名", max_length=191)
  
  
  class MyBook(models.Model):
      book_info = models.ForeignKey('BookInfo')
      buy_date = models.DateField("購入日", null=True)
      buy_user = models.CharField("購入希望者", max_length=191, blank=True)
      manager = models.CharField("管理責任者", max_length=191, blank=True)
      buy_at = models.CharField("購入場所", max_length=191, blank=True)
      purpose = models.TextField("購入目的", blank=True)
      money_source = models.CharField("資金源", max_length=191, blank=True)
      book_expire_at = models.DateField("本の賞味期限", null=True)
      created_at = models.DateTimeField(auto_now_add=True)
      updated_at = models.DateTimeField(auto_now=True)
  
  
  class BookInfo(models.Model):
      isbn = models.CharField("ISBN", primary_key=True, max_length=20)
      title = models.CharField("タイトル", max_length=191)
      title_kana = models.CharField("タイトル(カナ)", max_length=191, blank=True)
      sub_title = models.CharField("サブタイトル", max_length=191, blank=True)
      sub_title_kana = models.CharField("サブタイトル(カナ)", max_length=191, blank=True)
      series_name = models.CharField("シリーズ名", max_length=191, blank=True)
      series_name_kana = models.CharField("シリーズ名(カナ)", max_length=191, blank=True)
      author = models.CharField("著者", max_length=191, blank=True)
      author_kana = models.CharField("著者(カナ)", max_length=191, blank=True)
      publisher_name = models.CharField("出版社", max_length=191, blank=True)
      book_size = models.CharField("本サイズ", max_length=191, blank=True)
      item_caption = models.TextField("キャプション", blank=True)
      sales_date = models.DateField("発売日", null=True)
      item_price = models.IntegerField("価格", blank=True)
      image_url = models.URLField("画像URL", blank=True)
      genre_id = models.CharField("書籍ジャンル", max_length=191, blank=True)
  
subject: add blank=true at manager