refusal property
Refusal names why the set cannot be relied on, when it cannot: never loaded, held elsewhere, or a licence we do not hold. Non-empty means a lookup against this set will not answer, rather than answering clean.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? refusal;