code: @NonNull protected Integer getFragmentContainerViewRes() {
      return com.christianbahl.appkit.core.R.id.contentView;
    }
docs: <p>
  Provide the content view res id for the fragment container.
  </p>
  
  <p>
  <b>Default: </b> <code>R.id.contentView</code>
  </p>