old_contents: import datetime
  from flask import Markup
  from hashlib import md5
  from app import db
  from sqlalchemy import Table, Column, Integer, String, Boolean, ForeignKey, Date
  from sqlalchemy.orm import relationship
  from flask.ext.appbuilder.models.mixins import AuditMixin, BaseMixin, FileColumn, ImageColumn
  from flask.ext.appbuilder.filemanager import ImageManager
  from flask.ext.appbuilder import Base
  
  class Group(BaseMixin):
      id = Column(Integer, primary_key=True)
      name = Column(String(50), unique = True, nullable=False)
  
      def __repr__(self):
          return self.name
  
  
  class Contact(BaseMixin):
      id = Column(Integer, primary_key=True)
      name =  Column(String(150), unique = True, nullable=False)
      address = Column(String(564))
      birthday = Column(Date, nullable=True)
      personal_phone = Column(String(20))
      personal_celphone = Column(String(20))
      group_id = Column(Integer, ForeignKey('group.id'))
      group = relationship("Group")
  
      def __repr__(self):
          return self.name
          
  
new_contents: import datetime
  from flask import Markup
  from hashlib import md5
  from app import db
  from sqlalchemy import Table, Column, Integer, String, Boolean, ForeignKey, Date
  from sqlalchemy.orm import relationship
  from flask.ext.appbuilder.models.mixins import AuditMixin, BaseMixin, FileColumn, ImageColumn
  from flask.ext.appbuilder.filemanager import ImageManager
  from flask.ext.appbuilder import Base
  
  class Group(BaseMixin, Base):
      id = Column(Integer, primary_key=True)
      name = Column(String(50), unique = True, nullable=False)
  
      def __repr__(self):
          return self.name
  
  
  class Contact(BaseMixin, Base):
      id = Column(Integer, primary_key=True)
      name =  Column(String(150), unique = True, nullable=False)
      address = Column(String(564))
      birthday = Column(Date, nullable=True)
      personal_phone = Column(String(20))
      personal_celphone = Column(String(20))
      group_id = Column(Integer, ForeignKey('group.id'))
      group = relationship("Group")
  
      def __repr__(self):
          return self.name
          
  
subject: Update models.py