removeEventListener(
    type: string,
    handler: Function
  ) {
    invariant(
      ['change', 'memoryWarning'].indexOf(type) !== -1,
      'Trying to remove listener for unknown event: "%s"', type
    );
    if (!this._eventHandlers[type].has(handler)) {
      return;
    }
    this._eventHandlers[type].get(handler).remove();
    this._eventHandlers[type].delete(handler);
  }
Remove a handler by passing the `change` event type and the handler.

See http://facebook.github.io/react-native/docs/appstate.html#removeeventlistener