Create Shadows for internal nested protected class in Robolectric

I know that creation of custom shadows should be avoided, but my usecase is I have an Activity that implements a custom created widget which needs to be tested using Robolectric. While i call OnCreate from robolectric the test case fails because of Custom Widget.

So i need to write custom shadows for the class, my initial problem is my class to be referenced using org.robolectric.annotation.Implements.Implements() is an Inner nested protected class.

My code blocks looks as follows...

Class A{
  protected Class  B extends RadioGroup{

  }
}

I'm able to access A.class but not B.class in @Implements. Is there any way to access Class B from @Implements of Robolectric.

Thanks in advance any help is appreciated......