@Nullable
  private static String getIndexValueToReplace(@NotNull PyCallExpression call) {
    return Optional
      .of(call.getArguments())
      .map(ArrayUtil::getFirstElement)
      .map(firstArgument -> PyUtil.as(firstArgument, PyStringLiteralExpression.class))
      .map(PyStringLiteralExpression::getStringValue)
      .filter(PyNames::isIdentifier)
      .orElse(null);
  }
@Nullable
  private static String getIndexValueToReplace(@NotNull PyCallExpression call)