getEventAttribution(eventModel) {
        const _attribution = this.attributionBuilder.build({
            id: eventModel.get('attribution_id'),
            url: eventModel.get('attribution_url'),
            type: eventModel.get('attribution_type'),
            referrerSource: eventModel.get('referrer_source'),
            referrerMedium: eventModel.get('referrer_medium'),
            referrerUrl: eventModel.get('referrer_url')
        });

        if (_attribution.type && _attribution.type !== 'url') {
            // Find the right relation to use to fetch the resource
            const tryRelations = [
                eventModel.related('postAttribution'),
                eventModel.related('userAttribution'),
                eventModel.related('tagAttribution')
            ];
            for (const relation of tryRelations) {
                if (relation && relation.id) {
                    // We need to check the ID, because .related() always returs a model when eager loaded, even when the relation didn't exist
                    return _attribution.getResource(relation);
                }
            }
        }
        return _attribution.getResource(null);
    }
Returns the attribution resource for a given event model (MemberCreatedEvent / SubscriptionCreatedEvent), where the model has the required relations already loaded
You need to already load the 'postAttribution', 'userAttribution', and 'tagAttribution' relations
@param {Object} eventModel MemberCreatedEvent or SubscriptionCreatedEvent
@returns {import('./AttributionBuilder').AttributionResource|null}