Ionic 4 - ion-list adding filter to async

Ionic Framework ionic-v3
1

Is is possible to add filter to an ion-list that is using async?

I see example of using filter, but never with async. when i try, I get an error saying Unresolved Pipe filter

  <ion-searchbar placeholder="Search by Name" (ngModel)="searchTerm"></ion-searchbar>
  <ion-list *ngIf="results">
    <ion-item button *ngFor="let item of (results | async | filter:searchTerm)" routerDirection="forward" [routerLink]="['/hospital-details/'+ item.id]">
      <ion-label text-wrap>
        <h3>{{ item.name }}</h3>
      </ion-label>
    </ion-item>
  </ion-list>

But I see examples that are working:

   <ion-list>
      <ion-item  type="item-text-wrap" href="#/tab/friend/{{friend.id}}"
        ng-repeat="friend in friends | filter:search | limitTo:listlength">
        {{friend.name}}
      </ion-item>
    </ion-list>