private static boolean isOnlyLiterals(@NotNull PsiExpression operand) {
        if (operand instanceof PsiLiteralExpression) {
          return true;
        }
        else if (operand instanceof PsiPolyadicExpression polyadic) {
          for (PsiExpression expression : polyadic.getOperands()) {
            if (!isOnlyLiterals(expression)) return false;
          }
          return true;
        }
        else if (operand instanceof PsiParenthesizedExpression) {
          final PsiExpression expression = PsiUtil.skipParenthesizedExprDown(operand);
          if (expression != null && !isOnlyLiterals(expression)) return false;
          return true;
        }
        else {
          return false;
        }
      }
private static boolean isOnlyLiterals(@NotNull PsiExpression operand)