UiWatcher alternative in UiAutomator 2.0?

In UiAutomator 1.0, When UiSelector is unable to match any widget based on the specified criteria in the selector, then it will call UiWatcher. Similary what class we can use for BySelector in UiAutomator 2.0?

References:

1. https://developer.android.com/reference/android/support/test/uiautomator/package-summary
2. https://developer.android.com/reference/android/support/test/uiautomator/UiWatcher.html