Check if value is a valid DKIM

def _is_valid_dkim(self, value):
        """Check if value is a valid DKIM"""
        validator_dict = {'h': lambda val: val in ['sha1', 'sha256'],
                          's': lambda val: val in ['*', 'email'],
                          't': lambda val: val in ['y', 's'],
                          'v': lambda val: val == 'DKIM1',
                          'k': lambda val: val == 'rsa',
                          'n': lambda _: True,
                          'g': lambda _: True}

        splitted = value.split('\\;')
        found_key = False
        for splitted_value in splitted:
            sub_split = map(lambda x: x.strip(), splitted_value.split("=", 1))
            if len(sub_split) < 2:
                return False
            key, value = sub_split[0], sub_split[1]
            if key == "p":
                is_valid_key = self._is_valid_dkim_key(value)
                if not is_valid_key:
                    return False
                found_key = True
            else:
                is_valid_key = validator_dict.get(key, lambda _: False)(value)
                if not is_valid_key:
                    return False
        return found_key