case of
          the following filter
        </p>
<pre class="programlisting">%Coordinates% = "(10, 10)"</pre>
<p>
          the <code class="computeroutput"><span class="identifier">on_equality_relation</span></code>
          method will be called with <code class="computeroutput"><span class="identifier">name</span></code>
          argument being "Coordinates" and <code class="computeroutput"><span class="identifier">arg</span></code>
          being "(10, 10)".
        </p>
<div class="note"><table b