docs: def _rule_value(self):
          """ Parses the production rule::
                  value : TERM (',' TERM)*
  
              Returns list of string terms.
              """
  
          terms = [self._get_token()]
  
          # consume additional terms if available
          while self._lookahead_token() == ',':
              self._get_token()  # chomp the comma
              terms.append(self._get_token())
  
          return terms