Retrieves the congestion information of the incident/incidents from
        the output response

        Returns:
            congestion(namedtuple): List of named tuples of congestion info of
            the incident/incidents

def congestion(self):
        """Retrieves the congestion information of the incident/incidents from
        the output response

        Returns:
            congestion(namedtuple): List of named tuples of congestion info of
            the incident/incidents
        """
        resource_list = self.traffic_incident()
        congestion = namedtuple('congestion', 'congestion')
        if len(resource_list) == 1 and resource_list[0] is None:
            return None
        else:
            try:
                return [congestion(resource['congestion'])
                        for resource in resource_list]
            except (KeyError, TypeError):
                try:
                    return [congestion(resource['CongestionInfo'])
                            for resource in resource_list]
                except KeyError:
                    return None