docs: def detect_clause(parser, clause_name, tokens, as_filter_expr=True):
      """Helper function detects a certain clause in tag tokens list.
      Returns its value.
  
      """
      if clause_name in tokens:
          t_index = tokens.index(clause_name)
          clause_value = tokens[t_index + 1]
          if as_filter_expr:
              clause_value = parser.compile_filter(clause_value)
          del tokens[t_index:t_index + 2]
      else:
          clause_value = None
      return clause_value