old_contents: import DbHelper
  
  def singleton(_class):
      """
          a decorator that is used to implement singleton patten;
          Usage:
              @singleton
              class Foo:
                  pass
      """
      instances = {}
  
      def _getInstance(*args, **kwargs):
          if _class not in instances:
              instances[_class] = _class(*args, **kwargs)
          return instances[_class]
  
      return _getInstance
  
  
  def enum(*sequential):
      """
          pseudo Enum type;  Usage: EnumType=enum('key1','key2',...,)
      """
      enums = dict(zip(sequential, range(len(sequential))))
      return type('Enum', (), enums)
  
  
  def checkDB(fun):
      def _fun(self, *args):
          if self.db is None:
              self.db = DbHelper.DbHelper()
          fun(self, *args)
      return _fun
new_contents: import DbHelper
  
  def singleton(_class):
      """
          a decorator that is used to implement singleton patten;
          Usage:
              @singleton
              class Foo:
                  pass
      """
      instances = {}
  
      def _getInstance(*args, **kwargs):
          if _class not in instances:
              instances[_class] = _class(*args, **kwargs)
          return instances[_class]
  
      return _getInstance
  
  
  def enum(*sequential):
      """
          pseudo Enum type;  Usage: EnumType=enum('key1','key2',...,)
      """
      enums = dict(zip(sequential, range(len(sequential))))
      return type('Enum', (), enums)
  
  
  def checkDB(fun):
      def _fun(self, *args):
          if self.db is None:
              self.db = DbHelper.DbHelper()
          return fun(self, *args)
      return _fun
subject: Fix bug