code: @SuppressWarnings("unchecked")
    public static <T, A> ExtendedArray<T> extend(A array, ArrayAdapter<T, A> getter, T extra) {
      return new ExtendedArray<>(array, (ArrayAdapter<T, Object>) getter, extra);
    }
docs: Static wrapper that has a nicer generics signature.
  
  @param array Array to extend
  @param getter Getter for array
  @param extra Extra element
  @return Extended array