code: private ByteArrayContent postProcessContent(
        ByteArrayContent content, boolean isFirstRequest, boolean isLastRequest) throws IOException {
      if (isFirstRequest && isLastRequest) {
        return content;
      }
  
      String serializedRequest = Streams.readAll(content.getInputStream(), UTF_8);
  
      serializedRequest = trimStartEndElements(serializedRequest, isFirstRequest, isLastRequest);
  
      // The request is part of a set of incremental uploads, so pad to the required content
      // length. This is not necessary if all operations for the job are being uploaded in a
      // single request.
      int numBytes = serializedRequest.getBytes(UTF_8).length;
      int remainder = numBytes % REQUIRED_CONTENT_LENGTH_INCREMENT;
      if (remainder > 0) {
        int pad = REQUIRED_CONTENT_LENGTH_INCREMENT - remainder;
        serializedRequest = Strings.padEnd(serializedRequest, numBytes + pad, ' ');
      }
      return new ByteArrayContent(content.getType(), serializedRequest.getBytes(UTF_8));
    }
docs: Post-processes the request content to conform to the requirements of Google Cloud Storage.
  
  @param content the content produced by the {@link BatchJobUploadBodyProvider}.
  @param isFirstRequest if this is the first request for the batch job.
  @param isLastRequest if this is the last request for the batch job.