code: protected void processAddToBackstackFlag(String title, int flags, FragmentTransaction ft) {
          if ((flags & DO_NOT_ADD_TO_BACKSTACK) != DO_NOT_ADD_TO_BACKSTACK) {
              ft.addToBackStack(title);
          }
      }
docs: Processes Add to Backstack flag.
  <p/>
  Will not add the Fragment to the backstack if the
  {@link #DO_NOT_ADD_TO_BACKSTACK DO_NOT_ADD_TO_BACKSTACK} flag is found.
  
  @param title Title of the fragment
  @param flags Added flags to the Fragment configuration
  @param ft    Transaction to add to backstack from