Find usage for ELBv1 / Classic ELB and update the appropriate limits.

        :returns: number of Classic ELBs in use
        :rtype: int

def _find_usage_elbv1(self):
        """
        Find usage for ELBv1 / Classic ELB and update the appropriate limits.

        :returns: number of Classic ELBs in use
        :rtype: int
        """
        logger.debug("Checking usage for ELBv1")
        self.connect()
        lbs = paginate_dict(
            self.conn.describe_load_balancers,
            alc_marker_path=['NextMarker'],
            alc_data_path=['LoadBalancerDescriptions'],
            alc_marker_param='Marker'
        )
        for lb in lbs['LoadBalancerDescriptions']:
            self.limits['Listeners per load balancer']._add_current_usage(
                len(lb['ListenerDescriptions']),
                aws_type='AWS::ElasticLoadBalancing::LoadBalancer',
                resource_id=lb['LoadBalancerName'],
            )
            self.limits[
                'Registered instances per load balancer'
            ]._add_current_usage(
                len(lb['Instances']),
                aws_type='AWS::ElasticLoadBalancing::LoadBalancer',
                resource_id=lb['LoadBalancerName']
            )
        logger.debug('Done with ELBv1 usage')
        return len(lbs['LoadBalancerDescriptions'])