This is the ValueSet that contains all the codes in AdverseEventCausalityMethod (http://hl7.org/fhir/ValueSet/adverse-event-causality-method) and AdverseEventCausalityMethod (http://hl7.org/fhir/ValueSet/adverse-event-causality-method). E.g. what you have to deal with if you get resources containing codes in either of them