code: public void setProcessInputStream(OutputStream os) {
      if (input != null) {
        inputThread = createPump(input, os, true, nonBlockingRead);
      } else {
        Closeables.close(os);
      }
    }
docs: Set the <code>OutputStream</code> by means of which
  input can be sent to the process.
  @param os the <code>OutputStream</code>.