span>
  <span class="keyword">namespace</span> <span class="identifier">property_tree</span> <span class="special">{</span>
    <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Key<span class="special">,</span> <span class="keyword">typename</span> Data<span class="special">,</span> 
             <span class="keyword">typename</span> KeyCompare <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span cla