def last_modified(self):
        """Retrieves the last modified time stamp of the incident/incidents
        from the output response

        Returns:
            last_modified(namedtuple): List of named tuples of last modified
            time stamp of the incident/incidents
        """
        resource_list = self.traffic_incident()
        last_modified = namedtuple('last_modified', 'last_modified')
        if len(resource_list) == 1 and resource_list[0] is None:
            return None
        else:
            try:
                return [last_modified(resource['lastModified'])
                        for resource in resource_list]
            except (KeyError, TypeError):
                return [last_modified(resource['LastModifiedUTC'])
                        for resource in resource_list]