@classmethod<EOL><INDENT>def fix_timezone_separator(cls, timestr):<DEDENT>
tz_sep = cls.TIMEZONE_SEPARATOR.match(timestr)<EOL>if tz_sep is not None:<EOL><INDENT>return tz_sep.group(<NUM_LIT:1>) + tz_sep.group(<NUM_LIT:2>) + '<STR_LIT::>' + tz_sep.group(<NUM_LIT:3>)<EOL><DEDENT>return timestr<EOL>
Replace invalid timezone separator to prevent
        `dateutil.parser.parse` to raise.

        :return: the new string if invalid separators were found,
                 `None` otherwise