@property<EOL><INDENT>@memoize_method<EOL>def exceptions(self):<DEDENT>
ex = {}<EOL>for sd in self.root.xpath('<STR_LIT>'):<EOL><INDENT>bits = str(sd.text).split('<STR_LIT:U+0020>')<EOL>date = text_to_date(bits.pop(<NUM_LIT:0>))<EOL>ex.setdefault(date, []).extend([<EOL>_time_text_to_period(t)<EOL>for t in bits<EOL>])<EOL><DEDENT>return ex<EOL>
A dict of dates -> [Period time tuples] representing exceptions
        to the base recurrence pattern.