code: public static MetricDescriptor create(
        String name, String description, String unit, Type type, List<LabelKey> labelKeys) {
      Utils.checkListElementNotNull(Utils.checkNotNull(labelKeys, "labelKeys"), "labelKey");
      return new AutoValue_MetricDescriptor(
          name,
          description,
          unit,
          type,
          Collections.unmodifiableList(new ArrayList<LabelKey>(labelKeys)));
    }
docs: Creates a {@link MetricDescriptor}.
  
  @param name name of {@code MetricDescriptor}.
  @param description description of {@code MetricDescriptor}.
  @param unit the metric unit.
  @param type type of {@code MetricDescriptor}.
  @param labelKeys the label keys associated with the {@code MetricDescriptor}.
  @return a {@code MetricDescriptor}.
  @since 0.17