code: public static Hasher putMetricValue(Hasher h, MetricValue value) {
      Signing.putLabels(h, value.getLabelsMap());
      return h;
    }
docs: Updates {@code h} with the contents of {@code value}.
  
  @param h a {@link Hasher}
  @param value a {@code MetricValue} to be added to the hash
  @return the {@code Hasher}, to allow fluent-style usage