Ionic 4 - ion-list adding filter to async

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/'+]">
      <ion-label text-wrap>
        <h3>{{ }}</h3>

But I see examples that are working:

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