message: Fix `Map` handling in `declaration.ts`
diff: @@ -98,7 +98,7 @@ export class OptionDeclaration {
  const values = Object.keys(map).map(key => map[key]);
  if (map instanceof Map) {
  - value = map.has(key) ? map.get(key) : key;
  + value = map.has(key) ? map.get(key) : value;
  } else if (key in map) {
  value = map[key];
  } else if (values.indexOf(value) === -1 && errorCallback) {
  