code: public Container or(Container x) {
      if (x instanceof ArrayContainer) {
        return or((ArrayContainer) x);
      } else if (x instanceof BitmapContainer) {
        return or((BitmapContainer) x);
      }
      return or((RunContainer) x);
    }
docs: Computes the bitwise OR of this container with another (union). This container as well as the
  provided container are left unaffected.
  
  @param x other container
  @return aggregated container