Define a property that is set to true if the given token is found in
        the log file.  Uses the __contains__ method of the log file.

def token_scan(cls, result_key, token):
        """
        Define a property that is set to true if the given token is found in
        the log file.  Uses the __contains__ method of the log file.
        """
        def _scan(self):
            return token in self

        cls.scan(result_key, _scan)