iv class="line"><a name="l00020"></a><span class="lineno">   20</span>&#160;  <span class="keyword">friend</span> <span class="keyword">class </span>Topology;</div><div class="line"><a name="l00021"></a><span class="lineno">   21</span>&#160;  <span class="keyword">friend</span> <span class="keyword">class </span><a class="code" href="classtf_1_1Executor.html">Executor</a>;</div><div class="line"><a name="l00022"></a><span class="lineno">   22</span>&#160;  <span class="keyword">friend</span> <span class="k