code: static void serializeHeaders(
        HttpHeaders headers,
        StringBuilder logbuf,
        StringBuilder curlbuf,
        Logger logger,
        LowLevelHttpRequest lowLevelHttpRequest)
        throws IOException {
      serializeHeaders(headers, logbuf, curlbuf, logger, lowLevelHttpRequest, null);
    }
docs: Serializes headers to an {@link LowLevelHttpRequest}.
  
  @param headers HTTP headers
  @param logbuf log buffer or {@code null} for none
  @param curlbuf log buffer for logging curl requests or {@code null} for none
  @param logger logger or {@code null} for none. Logger must be specified if log buffer is
  specified
  @param lowLevelHttpRequest low level HTTP request where HTTP headers will be serialized to or
  {@code null} for none