private String toIndentedString(Object o) {
            if (o == null) {
                return "null";
            }
            return o.toString().replace("\n", "\n    ");
        }
Convert the given object to string with each line indented by 4 spaces
(except the first line).
core/src/test/java/com/alibaba/fastjson2/issues_2500/Issue2548.java