docs: public static void write004(Writer writer, Enumeration<Collector.MetricFamilySamples> mfs) throws IOException {
      /* See http://prometheus.io/docs/instrumenting/exposition_formats/
       * for the output format specification. */
      while(mfs.hasMoreElements()) {
        Collector.MetricFamilySamples metricFamilySamples = mfs.nextElement();
        writer.write("# HELP ");
        writer.write(metricFamilySamples.name);
        writer.write(' ');
        writeEscapedHelp(writer, metricFamilySamples.help);
        writer.write('\n');
  
        writer.write("# TYPE ");
        writer.write(metricFamilySamples.name);
        writer.write(' ');
        writer.write(typeString(metricFamilySamples.type));
        writer.write('\n');
  
        for (Collector.MetricFamilySamples.Sample sample: metricFamilySamples.samples) {
          writer.write(sample.name);
          if (sample.labelNames.size() > 0) {
            writer.write('{');
            for (int i = 0; i < sample.labelNames.size(); ++i) {
              writer.write(sample.labelNames.get(i));
              writer.write("=\"");
              writeEscapedLabelValue(writer, sample.labelValues.get(i));
              writer.write("\",");
            }
            writer.write('}');
          }
          writer.write(' ');
          writer.write(Collector.doubleToGoString(sample.value));
          if (sample.timestampMs != null){
            writer.write(' ');
            writer.write(sample.timestampMs.toString());
          }
          writer.write('\n');
        }
      }
    }