Python xml原代码求助

    for parser_name in parser_list + default_parser_list:
        try:
            return _create_parser(parser_name)
        except ImportError as e:
            import sys
            if parser_name in sys.modules:
                # The parser module was found, but importing it
                # failed unexpectedly, pass this exception through
             这一行代码是什么。。。。

except SAXReaderNotAvailable:
    # The parser module detected that it won't work properly,
    # so try the next one
    pass
看源代码不小心按错删除了。。。。急求，谢谢大家了