cial">::</span><span class="identifier">uint64_t</span>
    <span class="identifier">size</span><span class="special">(</span><span class="identifier">value_type</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">body</span><span class="special">);</span>
<span class="special">};</span>

<span class="keyword">static_assert</span><span class="special">(</span><span class="identifier">is_body</span><span class="special">&lt;</span><span class="identifier">Body