code: @Override
    public void write(byte[] record) throws IOException {
      Preconditions.checkNotNull(record);
  
      byte[] toWrite = record;
      if (this.recordDelimiter.isPresent()) {
        toWrite = Arrays.copyOf(record, record.length + 1);
        toWrite[toWrite.length - 1] = this.recordDelimiter.get();
      }
      if (this.prependSize) {
        long recordSize = toWrite.length;
        ByteBuffer buf = ByteBuffer.allocate(Longs.BYTES);
        buf.putLong(recordSize);
        toWrite = ArrayUtils.addAll(buf.array(), toWrite);
      }
      this.stagingFileOutputStream.write(toWrite);
      this.bytesWritten += toWrite.length;
      this.recordsWritten++;
    }
docs: Write a source record to the staging file
  
  @param record data record to write
  @throws java.io.IOException if there is anything wrong writing the record