docs: @VisibleForTesting
    static Metric createMetric(
        io.opencensus.metrics.export.MetricDescriptor metricDescriptor,
        List<LabelValue> labelValues,
        String domain,
        Map<LabelKey, LabelValue> constantLabels) {
      Metric.Builder builder = Metric.newBuilder();
      builder.setType(generateType(metricDescriptor.getName(), domain));
      Map<String, String> stringTagMap = Maps.newHashMap();
      List<LabelKey> labelKeys = metricDescriptor.getLabelKeys();
      for (int i = 0; i < labelValues.size(); i++) {
        String value = labelValues.get(i).getValue();
        if (value == null) {
          continue;
        }
        stringTagMap.put(labelKeys.get(i).getKey(), value);
      }
      for (Map.Entry<LabelKey, LabelValue> constantLabel : constantLabels.entrySet()) {
        String constantLabelKey = constantLabel.getKey().getKey();
        String constantLabelValue = constantLabel.getValue().getValue();
        constantLabelValue = constantLabelValue == null ? "" : constantLabelValue;
        stringTagMap.put(constantLabelKey, constantLabelValue);
      }
      builder.putAllLabels(stringTagMap);
      return builder.build();
    }