@Nullable
  private static String getIndexValueToReplace(@NotNull PySubscriptionExpression subscription) {
    return Optional
      .ofNullable(subscription.getIndexExpression())
      .map(indexExpression -> PyUtil.as(indexExpression, PyStringLiteralExpression.class))
      .map(PyStringLiteralExpression::getStringValue)
      .filter(PyNames::isIdentifier)
      .orElse(null);
  }
@Nullable
  private static String getIndexValueToReplace(@NotNull PySubscriptionExpression subscription)