old_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  import datetime
  from books import db
  
  
  class Book(db.Document):
      _id = db.StringField(required=True)
      created_time = db.DateTimeField(default=datetime.datetime.now, required=True)
      body = db.StringField(required=True)
  
new_contents: #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  import datetime
  from books import db
  
  
  class Book(db.Document):
      book_id = db.StringField(required=True)
      book_title = db.StringField(required=True)
      book_author =
      book_translator =
      book_img =
      book_url =
      book_summary =
      book_publisher =
      book_isbn =
      book_tags = ListField()
      book_add_time = db.DateTimeField(default=datetime.datetime.now, required=True)
  
  class Tag(db.EmbeddedDocument):
      tag_name =
      tag_title =
      tag_count =
  
  class Resource(db.EmbeddedDocument):
  
subject: update book model