This is the ValueSet that contains all the codes in Questionnaire answer constraints value set (http://hl7.org/fhir/uv/sdc/ValueSet/questionnaire-answer-constraint) and Questionnaire answer constraints value set (http://hl7.org/fhir/uv/sdc/ValueSet/questionnaire-answer-constraint). E.g. what you have to deal with if you get resources containing codes in either of them