code: @Override
    public FSDataOutputStream append(Path hadoopPath, int bufferSize, Progressable progress)
        throws IOException {
  
      long startTime = System.nanoTime();
      Preconditions.checkArgument(hadoopPath != null, "hadoopPath must not be null");
  
      logger.atFine().log("GHFS.append: %s, bufferSize: %d (ignored)", hadoopPath, bufferSize);
  
      long duration = System.nanoTime() - startTime;
      increment(Counter.APPEND);
      increment(Counter.APPEND_TIME, duration);
      throw new IOException("The append operation is not supported.");
    }
docs: Appends to an existing file (optional operation). Not supported.
  
  @param hadoopPath The existing file to be appended.
  @param bufferSize The size of the buffer to be used.
  @param progress For reporting progress if it is not null.
  @return A writable stream.
  @throws IOException if an error occurs.