http://hl7.org/fhir/StructureDefinition/valueset-unclosed|4.0.1

Marks that the expansion is incomplete, and values other than those listed may be valid. This may be used because post-coordinated codes are allowed, and no practical expansion can be produced.
element_idtypes
Extension
Extension.extension
Extension.url
Extension.value[x]
Extension
Extension.id
Extension.extension
Extension.url
Extension.value[x]