depth_first_search</tt> because the <tt class="docutils literal">root_vertex</tt> argument,
<tt class="docutils literal">&quot;hello&quot;</tt>, doesn't meet the <a class="reference internal" href="#parameter-table">requirement</a> that it match the
<tt class="docutils literal">graph</tt> parameter's vertex descriptor type.  Instead, this call
should just invoke our new overload.  To take the original
<tt class="docutils literal">depth_first_search</tt> overload out of contention, we need to tell
the librar