This is the ValueSet that contains all the codes in CRD Metric Data Source Value Set (http://hl7.org/fhir/us/davinci-crd/ValueSet/metricDataSource) and CRD Metric Data Source Value Set (http://hl7.org/fhir/us/davinci-crd/ValueSet/metricDataSource). E.g. what you have to deal with if you get resources containing codes in either of them