code: def add_parameters(url, parameters):
      
      if parameters:
          sep = '&' if '?' in url else '?'
          return '{0}{1}{2}'.format(url, sep, urlencode(parameters))
      return url
docs: Appends URL-encoded parameters to the base URL. It appends after '&' if
      '?' is found in the URL; otherwise it appends using '?'. Keep in mind that
      this tag does not take into account the value of existing params; it is
      therefore possible to add another value for a pre-existing parameter.
  
      For example::
  
          {% url 'this_view' as current_url %}
          {% with complete_url=current_url|add_parameters:request.GET %}
              The <a href="{% url 'other' %}?next={{ complete_url|urlencode }}">
              other page</a> will redirect back to the current page (including
              any GET parameters).
          {% endwith %}