<span class="keyword">struct</span> <span class="identifier">is_message</span><span class="special">&lt;</span><span class="identifier">basic_message</span><span class="special">&lt;</span><span class="identifier">Headers</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">&gt;&gt;:</span> <span class="keyword">public</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">true_type</span> <span class="special">{};</span>
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