case, we are attaching to the <code class="computeroutput"><span class="identifier">xml</span></code> rule.
        </p>
<p>
          <code class="computeroutput"><span class="identifier">handler</span></code> is the actual error
          handling function. It expects 4 arguments:
        </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                  <p>
                    Arg
                  </p>
                </th>
<th>
                  