title: Filter in custom Django tag?
body: <p>I created a custom tag, that accepts a parameter:</p>
  
  <pre><code>{% panel "most" %}
  </code></pre>
  
  <p>I would use the <code>add</code> to the parameter: </p>
  
  <pre><code>{% panel "most"|add:"_people" %}
  </code></pre>
  
  <p>I expect the parameter will be "most_people", but instead it is "most"|add:"_people". It seems that filters are not invoked inside custom tags. How to make them work?</p>