docs: def by_skills(queryset, skill_string=None):
    """ Filter queryset by a comma delimeted skill list """
    if skill_string:
      operator, items = get_operator_and_items(skill_string)
      q_obj = SQ()
      for s in items:
        if len(s) > 0:
          q_obj.add(SQ(skills=s), operator)
      queryset = queryset.filter(q_obj)
    return queryset