      def to_representation(self, value):
          if not value:
              return None
  
          if self.format is None:
              return value
  
          # Applying a `DateField` to a datetime value is almost always
          # not a sensible thing to do, as it means naively dropping
          # any explicit or implicit timezone info.
 
</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     url_field_name = api_settings.URL_FIELD_NAME
 </s> add     url_field_name = None </s> remove         if self.use_url:
 </s> add         if use_url: </s> remove         if self.format.lower() == ISO_8601:
 </s> add         if output_format.lower() == ISO_8601:
        if output_format is None:
      def to_representation(self, value):
          if not value:
              return None
  
        if output_format is None:
              return value
  
          # Applying a `DateField` to a datetime value is almost always
          # not a sensible thing to do, as it means naively dropping
          # any explicit or implicit timezone info.
keep keep keep keep replace keep keep keep keep keep
 Access settings lazily, not at module import 
rest_framework/fields.py