r>
<td>
                <p>
                  <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">on_timer</span><span class="special">()</span></code>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  The implementation calls this function every time the internal
                  timer expires. The policy object may optionally use this opportunity
                  to calculate elaps