WriteStream concept.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
                    <code class="computeroutput"><span class="identifier">msg</span></code>
                  </p>
                </td>
<td>
                  <p>
                    The message to write. The object must remain valid at least until
                    the handler is called; ownership is not transferred.
                  </p>
                </td>
</tr>
<tr>
<td>
                  <p>
  