docs: def to_content_range_header(self, length):
          """Converts the object into `Content-Range` HTTP header,
          based on given length
          """
          range_for_length = self.range_for_length(length)
          if range_for_length is not None:
              return "%s %d-%d/%d" % (
                  self.units,
                  range_for_length[0],
                  range_for_length[1] - 1,
                  length,
              )
          return None