This is the ValueSet that contains all the codes in Observation Extract Relationship Value Set (http://hl7.org/fhir/uv/sdc/ValueSet/observation-extract-relationship) and Observation Extract Relationship Value Set (http://hl7.org/fhir/uv/sdc/ValueSet/observation-extract-relationship). E.g. what you have to deal with if you get resources containing codes in either of them