This is the ValueSet that contains all the codes in FR Core ValueSet relation type (https://hl7.fr/ig/fhir/core/ValueSet/fr-core-vs-relation-type) and FR Core ValueSet relation type (https://hl7.fr/ig/fhir/core/ValueSet/fr-core-vs-relation-type). E.g. what you have to deal with if you get resources containing codes in either of them