docs: def pass_multipart(with_completed=False):
      """Decorate to retrieve an object."""
      def decorate(f):
          @wraps(f)
          def inner(self, bucket, key, upload_id, *args, **kwargs):
              obj = MultipartObject.get(
                  bucket, key, upload_id, with_completed=with_completed)
              if obj is None:
                  abort(404, 'uploadId does not exists.')
              return f(self, obj, *args, **kwargs)
          return inner
      return decorate