Angularfire2中AngularFireList.query属性的用途是什么？

Question

....
import { AngularFireDatabase, AngularFireList } from 'angularfire2/database';

export class CustomerService {

constructor(private firebase: AngularFireDatabase) { }
customerList: AngularFireList<any>;

getCustomers() {
    this.customerList = this.firebase.list('customers');
    return this.customerList.snapshotChanges();
  }

queryList(searchText) {   
    this.customerList.query = ????;
  }

在上面，例如可以使用 query 属性进行数据过滤吗？