bbPress.org

Hi,
you provided me several months ago with a function that displays a search field in the bbp forum:

function rk_bbp_search_form(){
    if ( bbp_allow_search()) {
      ?>
      <div class="bbp-search-form">
      <?php bbp_get_template_part( 'form', 'search' ); ?>
      </div>
      <?php
      } }
  add_action( 'bbp_template_before_single_forum', 'rk_bbp_search_form' );
  add_action( 'bbp_template_before_single_topic', 'rk_bbp_search_form' );

Although i appreciate this help, i have found that the relevansi search is better at finding all forum topics on my website. They have provided the code here to display a search box.
I would really like this to replace the one in the function above but am having a problem doing this.
I know this is cheeky, but can you help?