How to make an Ionic Collapse?

Question

I’m trying to make a collapse and it’s like this:

HTML

<ion-content>

{{topical.}}

<ion-item *ngFor="let aulas of topicos.get_classes" [hidden]="deixainvisivel" menuClose ion-item (click)="openClass(aulas.id)">{{aulas.name}} <b>{{aulas.time}}</b></ion-item>

TS

  Collapse(id){
console.log(id)
this.idtopic = id;
this.deixainvisivel = !this.deixainvisivel;

}

The problem is that it closes all "topics", I have to find a way to close only those who have the ID of the item Divider