def parse(self, string, evaluate_result=True):
        '''Match my format to the string exactly.

        Return a Result or Match instance or None if there's no match.
        '''
        m = self._match_re.match(string)
        if m is None:
            return None

        if evaluate_result:
            return self.evaluate_result(m)
        else:
            return Match(self, m)
Match my format to the string exactly.

        Return a Result or Match instance or None if there's no match.