old_contents: from sqlalchemy import orm
  from datetime import datetime
  from infosystem.database import db
  from infosystem.subsystem.tag import resource
  from infosystem.common.subsystem import entity
  
  
  class Notification(entity.Entity, db.Model):
  
      attributes = ['id', 'user_id', 'date', 'subject', 'body', 'read_date']
  
      user_id = db.Column(
          db.CHAR(32), db.ForeignKey("user.id"), nullable=False)
      date = db.Column(db.Date, nullable=False)
      subject = db.Column(db.String(50), nullable=False)
      body = db.Column(db.String(250), nullable=False)
      read_date = db.Column(db.Date, nullable=True)
      tags = orm.relationship(
          "NotificationTag", backref=orm.backref('notification'),
          cascade='delete,delete-orphan,save-update')
  
      def __init__(self, id, user_id, date, subject, body, read_date=None):
          super().__init__(id)
          self.user_id = user_id
          self.date = datetime.strptime(date, entity.DATETIME_FMT)
          self.subject = subject
          self.body = body
          if (read_date is not None):
              self.read_date = datetime.strptime(read_date, entity.DATETIME_FMT)
  
      @classmethod
      def embedded(cls):
          return ['tags']
  
  
  class NotificationTag(resource.Tag, db.Model):
  
      notification_id = db.Column(
          db.CHAR(32), db.ForeignKey("notification.id"), nullable=False)
  
      def __init__(self, id, label, notification_id):
          super().__init__(id, label)
          self.notification_id = notification_id
  
new_contents: from sqlalchemy import orm
  from datetime import datetime
  from infosystem.database import db
  from infosystem.subsystem.tag import resource
  from infosystem.common.subsystem import entity
  
  
  class Notification(entity.Entity, db.Model):
  
      attributes = ['id', 'user_id', 'date', 'subject', 'body', 'read_date']
  
      user_id = db.Column(
          db.CHAR(32), db.ForeignKey("user.id"), nullable=False)
      date = db.Column(db.Date, nullable=False)
      subject = db.Column(db.String(50), nullable=False)
      body = db.Column(db.String(250), nullable=False)
      read_date = db.Column(db.Date, nullable=True)
      tags = orm.relationship(
          "NotificationTag", backref=orm.backref('notification'),
          cascade='delete,delete-orphan,save-update')
  
      def __init__(self, id, user_id, date, subject, body, read_date=None):
          super().__init__(id)
          self.user_id = user_id
          self.date = datetime.strptime(date, entity.DATETIME_FMT)
          self.subject = subject
          self.body = body
          if (read_date is not None):
              self.read_date = datetime.strptime(read_date, entity.DATETIME_FMT)
  
      @classmethod
      def embedded(cls):
          return ['tags']
  
  
  class NotificationTag(resource.Tag, db.Model):
  
      attributes = ['label']
  
      notification_id = db.Column(
          db.CHAR(32), db.ForeignKey("notification.id"), nullable=False)
  
      def __init__(self, id, label, notification_id):
          super().__init__(id, label)
          self.notification_id = notification_id
  
subject: Remove id from return json