adapter.fetch is not a function when using TORII for Auth in 3.0.0-rc6 about emberfire HOT 1 CLOSED

import ToriiFirebaseAdapter from 'emberfire/torii-adapters/firebase';
import Ember from 'ember';

export default ToriiFirebaseAdapter.extend({

    /**
   * Restore existing authenticated session
   *
   * @return {Promise}
   */
  fetch() {
    return this.fetchAuthState_()
      .then((user) => {
        if (!user) {
          return this.fetchRedirectState_();
        }
        return user;
      })
      .then((user) => {
        if (!user) {
          return Ember.RSVP.reject(new Error('No session available'));
        }
        return this.open(user);
      })
      .catch((err) => Ember.RSVP.reject(err));
  },


  /**
   * Fetches the redirect user, if any.
   *
   * @return {!Promise<?firebase.User>}
   * @private
   */
  async fetchRedirectState_() {
    let auth = await this.get('firebaseApp').auth();
    return auth.getRedirectResult()
      .then(result => result.user);
  },


  /**
   * Promisifies the first value of onAuthStateChanged
   *
   * @return {!Promise<?firebase.User>}
   * @private
   */
  async fetchAuthState_() {
    return new Ember.RSVP.Promise(async (resolve, reject) => {
      let auth = await this.get('firebaseApp').auth();
      const unsub = auth.onAuthStateChanged((user) => {
        unsub();
        resolve(user);
      },
      (err) => {
        unsub();
        reject(err);
      });
    });
  },

});