This is the ValueSet that contains all the codes in AccessAuditTrailEventType (http://fhir.ch/ig/ch-atc/ValueSet/AccessAuditTrailEventType) and AccessAuditTrailEventType (http://fhir.ch/ig/ch-atc/ValueSet/AccessAuditTrailEventType). E.g. what you have to deal with if you get resources containing codes in either of them