Find usage for ELBv2 / Application LB and update the appropriate limits.

        :returns: number of Application LBs in use
        :rtype: int

def _find_usage_elbv2(self):
        """
        Find usage for ELBv2 / Application LB and update the appropriate limits.

        :returns: number of Application LBs in use
        :rtype: int
        """
        logger.debug('Checking usage for ELBv2')
        conn2 = client(
            'elbv2',
            config=Config(retries={'max_attempts': ELBV2_MAX_RETRY_ATTEMPTS}),
            **self._boto3_connection_kwargs
        )
        logger.debug("Connected to %s in region %s (with max retry attempts "
                     "overridden to %d)", 'elbv2',
                     conn2._client_config.region_name, ELBV2_MAX_RETRY_ATTEMPTS)
        # Target groups
        tgroups = paginate_dict(
            conn2.describe_target_groups,
            alc_marker_path=['NextMarker'],
            alc_data_path=['TargetGroups'],
            alc_marker_param='Marker'
        )
        self.limits['Target groups']._add_current_usage(
            len(tgroups['TargetGroups']),
            aws_type='AWS::ElasticLoadBalancingV2::TargetGroup'
        )
        # ALBs
        lbs = paginate_dict(
            conn2.describe_load_balancers,
            alc_marker_path=['NextMarker'],
            alc_data_path=['LoadBalancers'],
            alc_marker_param='Marker'
        )
        logger.debug(
            'Checking usage for each of %d ALBs', len(lbs['LoadBalancers'])
        )
        alb_count = 0
        nlb_count = 0
        for lb in lbs['LoadBalancers']:
            if lb.get('Type') == 'network':
                nlb_count += 1
            else:
                alb_count += 1
                self._update_usage_for_alb(
                    conn2,
                    lb['LoadBalancerArn'],
                    lb['LoadBalancerName']
                )
        self.limits['Network load balancers']._add_current_usage(
            nlb_count,
            aws_type='AWS::ElasticLoadBalancing::NetworkLoadBalancer'
        )
        logger.debug('Done with ELBv2 usage')
        return alb_count