@VisibleForTesting
  static synchronized @NotNull PyPIPackageCache getInstance(@NotNull Path pathToCache) {
    if (ourInstance == null) {
      ourInstance = PyAbstractPackageCache.load(PyPIPackageCache.class, new PyPIPackageCache(), pathToCache);
    }
    return ourInstance;
  }
@VisibleForTesting
  static synchronized @NotNull PyPIPackageCache getInstance(@NotNull Path pathToCache)