delete(): void {
   if (confirm('Are you sure you want to delete this book?')) {
     // delete
     this.apollo.mutate({
       mutation: deleteBookMutation,
       variables: { id: this.model.id },
       refetchQueries: [{
         query: getBooksQuery
       }]
     })
     .subscribe( (data: any) => {
     });
this.reset();
   }
 }