              self._user_settings = user_settings
          self.defaults = defaults or DEFAULTS
          self.import_strings = import_strings or IMPORT_STRINGS
  
      def __getattr__(self, attr):
          if attr not in self.defaults.keys():
              raise AttributeError("Invalid API setting: '%s'" % attr)
  
 
</s> remove         self.user_settings = user_settings or {}
 </s> add         if user_settings:
            self._user_settings = user_settings </s> remove USER_SETTINGS = getattr(settings, 'REST_FRAMEWORK', None)
 </s> add  </s> remove         if self.format is None:
 </s> add         output_format = getattr(self, 'format', api_settings.TIME_FORMAT)

        if output_format is None: </s> remove         self.use_url = kwargs.pop('use_url', self.use_url)
 </s> add         if 'use_url' in kwargs:
            self.use_url = kwargs.pop('use_url')
    @property
    def user_settings(self):
        if not hasattr(self, '_user_settings'):
            self._user_settings = getattr(settings, 'REST_FRAMEWORK', {})
        return self._user_settings

              self._user_settings = user_settings
          self.defaults = defaults or DEFAULTS
          self.import_strings = import_strings or IMPORT_STRINGS
  
    @property
    def user_settings(self):
        if not hasattr(self, '_user_settings'):
            self._user_settings = getattr(settings, 'REST_FRAMEWORK', {})
        return self._user_settings

      def __getattr__(self, attr):
          if attr not in self.defaults.keys():
              raise AttributeError("Invalid API setting: '%s'" % attr)
  
keep keep keep add keep keep keep keep
 Access settings lazily, not at module import 
rest_framework/settings.py