n><span class="identifier">indent</span> <span class="special">&lt;&lt;</span> <span class="identifier">json</span><span class="special">::</span><span class="identifier">serialize</span><span class="special">(</span><span class="identifier">it</span><span class="special">-&gt;</span><span class="identifier">key</span><span class="special">())</span> <span class="special">&lt;&lt;</span> <span class="string">" : "</span><span class="special">;</span>
                <span class="identifier">pretty_print</sp