@NotNull
  public static PyBuiltinCache getInstance(@Nullable PsiElement reference) {
    if (reference != null) {
      try {
        Sdk sdk = findSdkForFile(reference.getContainingFile());
        if (sdk != null) {
          return PythonSdkPathCache.getInstance(reference.getProject(), sdk).getBuiltins();
        }
      }
      catch (PsiInvalidElementAccessException ignored) {
      }
    }
    return DUD_INSTANCE; // a non-functional fail-fast instance, for a case when skeletons are not available
  }
@NotNull
  public static PyBuiltinCache getInstance(@Nullable PsiElement reference)