pan class="comment">// Check each field promised in the "Trailer" header and output it</span>
    <span class="keyword">for</span><span class="special">(</span><span class="keyword">auto</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">name</span> <span class="special">:</span> <span class="identifier">token_list</span><span class="special">{</span><span class="identifier">msg</span><span class="special">[</span><span class="identifier">field</span><span c