public AutocompleteTags autocompleteTags() { // returns default to not break compat
    return new AutocompleteTags() {
      @Override public Call<List<String>> getKeys() {
        return Call.emptyList();
      }

      @Override public Call<List<String>> getValues(String key) {
        return Call.emptyList();
      }

      @Override public String toString() {
        return "EmptyAutocompleteTags{}";
      }
    };
  }
A component that provides storage interfaces used for spans and aggregations. Implementations are
free to provide other interfaces, but the ones declared here must be supported.

@see InMemoryStorage
zipkin/src/main/java/zipkin2/storage/StorageComponent.java