old_contents: from google.appengine.api import users
  from model import User
  
  def create_user(google_user):
      user = User(
          google_user=google_user,
      )
      user.put()
      return user
  
  def get_current_user_model():
      return get_user_model_for(users.get_current_user())
  
  def get_user_model_for(google_user=None):
      return User.all().filter('google_user =', google_user).get()
  
  def get_user_model_by_id_or_nick(id_or_nick):
      if id_or_nick.isdigit():
          return User.get_by_id(int(id_or_nick))
      else:
          return User.all().filter('nickname_lower = ', id_or_nick.lower()).get()
new_contents: from google.appengine.api import users
  from model import User
  
  def create_user(google_user):
      user = User(
          google_user=google_user
      )
      user.put()
      return user
  
  def get_current_user_model():
      return get_user_model_for(users.get_current_user())
  
  def get_user_model_for(google_user=None):
      return User.all().filter('google_user =', google_user).get()
  
  def get_user_model_by_id_or_nick(id_or_nick):
      if id_or_nick.isdigit():
          return User.get_by_id(int(id_or_nick))
      else:
          return User.all().filter('nickname_lower = ', id_or_nick.lower()).get()
subject: Fix potential issue when creating users