n class="special">{</span> <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> <span class="special">}</span>
        <span class="keyword">bool</span> <span class="identifier">on_null</span><span class="special">(</span> <span class="identifier">error_code</span><span class="special">&amp;</span> <span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> <sp