Not able to add icon with label to Fab button in ionic 4

Ionic Framework
1 
`<ion-fab vertical="bottom" horizontal="end" slot="fixed">
    <ion-fab-button>
      <ion-icon name="add"></ion-icon>
    </ion-fab-button>
    <ion-fab-list side="top">
      <ion-fab-button routerLink="/add-asset">
          <ion-label>Assets</ion-label>
          <ion-icon name="laptop"></ion-icon>
      </ion-fab-button>
      <ion-fab-button routerLink="/asset-category">
        <ion-icon name="laptop"></ion-icon>
        <ion-label>Category</ion-label>
      </ion-fab-button>
    </ion-fab-list>
  </ion-fab>
`

css:
ion-fab-button {
overflow: visible;
position: relative;
ion-label {
position: absolute;
top: 0px;
right: 40px;
color: rgb(156, 39, 39);
background-color: rgba(0,0,0,0.7);
line-height: 24px;
padding: 4px 8px;
border-radius: 4px;
}
contain: layout;
}