"supportgroup" object has "manager" attribute linked to "manager"object. (see attached file : suppor

[jun lee]

"supportgroup" object has "manager" attribute linked to "manager"object. (see attached file : supportgroup.jpg, manager.jpg)

I addded an automation rule like example 4 (https://confluence.atlassian.com/jirakb/auto-populate-approvers-from-insight-objects-1072474097.html)
{
"fields": {
"ENM_USER_MULTI": {{supportgroup object.manager.flatten.asJsonObjectArray("id")}}
}
}

However it doesn't work. Audit log shows " Edit issue
Error while parsing additional fields. Not valid JSON. "

What is a problem?