old_contents: """
      User Model
  """
  from barter import db
  
  
  class User(db.Document):
      username = db.StringField(required=True)
      email = db.EmailField(required=True)
      password = db.StringField(required=True)
      nickname = db.StringField(max_length=50)
      nationality = db.StringField(max_length=50)
      location = db.StringField(max_length=50)
      sex = db.BinaryField(max_bytes=2)
      age = db.IntField(min_value=0, max_value=150)
      introduction = db.StringField(max_length=500)
      teach_lan = db.ListField(field=db.StringField)
      learn_lan = db.ListField(field=db.StringField)
  
new_contents: """
      User Model
  """
  from barter import db
  
  
  class User(db.Document):
      username = db.StringField(required=True)
      email = db.EmailField(required=True)
      password = db.StringField(required=True)
      nickname = db.StringField(max_length=50)
      nationality = db.StringField(max_length=50)
      location = db.StringField(max_length=50)
      sex = db.BinaryField(max_bytes=2)
      age = db.IntField(min_value=0, max_value=150)
      introduction = db.StringField(max_length=500)
      teach_lan = db.ListField(field=db.StringField)
      learn_lan = db.ListField(field=db.StringField)
      profile_completed = db.BooleanField()
  
subject: update User