@NotNull
  @Override
  protected Maybe<String> translate(@Nullable PyExpression ref) {
    if (ref instanceof PyNoneLiteralExpression) {
      return new Maybe<>(PyNames.NONE);
    }
    else if (ref != null) {
      final String name = ref.getName();
      return name != null ? new Maybe<>(name) : unknown;
    }
    return none;
  }
@NotNull
  @Override
  protected Maybe<String> translate(@Nullable PyExpression ref)