refusal property
Refusal is why the set could not be consulted, when it could not: never loaded, held elsewhere, or a source we hold no licence for. Non-empty means Hit must not be read as an answer.
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;