invalidate(data) {
    return this.get('torii')
      .close(this._provider, data)
      .then(() => {
        delete this._provider;
      });
  }
Closes the torii provider. If the provider is successfully closed, this
    method returns a resolving promise, otherwise it will return a rejecting
    promise, thus intercepting session invalidation.

    @memberof ToriiAuthenticator
    @method invalidate
    @return {Promise} A promise that when it resolves results in the session being invalidated
    @public