code: def piwik(parser, token):
      
      bits = token.split_contents()
      if len(bits) > 1:
          raise TemplateSyntaxError("'%s' takes no arguments" % bits[0])
      return PiwikNode()
docs: Piwik tracking template tag.
  
      Renders Javascript code to track page visits.  You must supply
      your Piwik domain (plus optional URI path), and tracked site ID
      in the ``PIWIK_DOMAIN_PATH`` and the ``PIWIK_SITE_ID`` setting.
  
      Custom variables can be passed in the ``piwik_vars`` context
      variable.  It is an iterable of custom variables as tuples like:
      ``(index, name, value[, scope])`` where scope may be ``'page'``
      (default) or ``'visit'``.  Index should be an integer and the
      other parameters should be strings.