an> <span class="special">&amp;</span><span class="special">,</span> <a class="link" href="../boost/property_tree/basic_ptree.html" title="Class template basic_ptree">basic_ptree</a><span class="special">&lt;</span> <span class="identifier">K</span><span class="special">,</span> <span class="identifier">D</span><span class="special">,</span> <span class="identifier">C</span> <span class="special">&gt;</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">const</span> 