This is the ValueSet that contains all the codes in CDex Identifier Types Value Set (http://hl7.org/fhir/us/davinci-cdex/ValueSet/cdex-identifier-types) and CDex Identifier Types Value Set (http://hl7.org/fhir/us/davinci-cdex/ValueSet/cdex-identifier-types). E.g. what you have to deal with if you get resources containing codes in either of them