new_contents: form models.user import UserModel
  import tornado.gen
  
  class OAuthService():
      m_user = UserModel()
      
      def __init__(self):
          pass
        
      @tornado.gen.engine
      def update_gitlab_token(self,user_id,token=None,callback=None):
          user = yield tornado.gen.Task(m_user.update,{"_id":user_id},{"$set":{"gitlab_token":token}})
          callback(user)
  
subject: Update oauth.py