docs: public Iterable<String> getAllSortedTypeNames() {
      synchronized (lock) {
        if (lazyAllSortedTypeNames == null) {
          lazyAllSortedTypeNames =
              Stream.concat(BUILTIN_TYPES.keySet().stream(), descriptors.keySet().stream())
                  .sorted()
                  .collect(toImmutableList());
        }
        return lazyAllSortedTypeNames;
      }
    }