docs: @VisibleForTesting
    static LabelDescriptor createLabelDescriptor(LabelKey labelKey) {
      LabelDescriptor.Builder builder = LabelDescriptor.newBuilder();
      builder.setKey(labelKey.getKey());
      builder.setDescription(labelKey.getDescription());
      // Now we only support String tags
      builder.setValueType(ValueType.STRING);
      return builder.build();
    }