code: private static void printMetricHeader(final PrintWriter writer, final String metric,
        final long timestamp) {
      writer.print(metric);
      writer.print(' ');
      writer.print(timestamp / 1000L);
      writer.print(' ');
    }
docs: Helper method to write metric name and timestamp.
  @param writer The writer to which to write.
  @param metric The metric name.
  @param timestamp The timestamp.