code: def RegisterParser(cls, parser_class):
      
      parser_name = parser_class.NAME.lower()
      if parser_name in cls._parser_classes:
        raise KeyError('Parser class already set for name: {0:s}.'.format(
            parser_class.NAME))
  
      cls._parser_classes[parser_name] = parser_class
docs: Registers a parser class.
  
      The parser classes are identified based on their lower case name.
  
      Args:
        parser_class (type): parser class (subclass of BaseParser).
  
      Raises:
        KeyError: if parser class is already set for the corresponding name.