code: public final Ix<T> switchIfEmpty(Iterable<? extends T> other) {
          return new IxSwitchIfEmpty<T>(this, nullCheck(other, "other is null"));
      }
docs: Emits the elements of the other sequence if this sequence is empty.
  <p>
  The result's Iterator forwards calls of remove() to this' or the other's Iterator.
  @param other the other Iterable instance, not null
  @return the new Ix instance
  @throws NullPointerException if other is null
  @since 1.0