span class="keyword">void</span> <a class="link" href="../boost/property_tree/xml_parser/read__1_3_33_10_11_1_1_1_1.html" title="Function template read_xml"><span class="identifier">read_xml</span></a><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_istream</span><span class="special">&lt;</span> <span class="keyword">typename</span> <span class="identifier">Ptree</span><span class="special">::</span><span class="identifier">key_t