code: public final int indexOfNavigationPreference(
              @NonNull final NavigationPreference navigationPreference) {
          Condition.INSTANCE
                  .ensureNotNull(navigationPreference, "The navigation preference may not be null");
          return navigationPreferences.indexOf(navigationPreference);
      }
docs: Returns the index of a specific navigation preference among all navigation preferences, which
  are contained by the adapter.
  
  @param navigationPreference
  The navigation preference, whose index should be returned, as an instance of the
  class {@link NavigationPreference}. The navigation preference may not be null
  @return The index of the given navigation preference as an {@link Integer} value or -1, if
  the navigation preference is not contained by the adapter