ember function. If this is not movable or not copyable, the containing
                  message will be not movable or not copyable.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">B</span><span class="special">::</span><span class="identifier">reader</span></code>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  If present, indicates that the body