/span>
    <span class="identifier">error</span>
<span class="special">};</span>

<span class="comment">// A trivial sink backend that requires no thread synchronization</span>
<span class="keyword">class</span> <span class="identifier">my_backend</span> <span class="special">:</span>
    <span class="keyword">public</span> <span class="identifier">sinks</span><span class="special">::</span><span class="identifier">basic_sink_backend</span><span class="special">&lt;</span> <span class="identifier">sinks</sp