docs: private Factory<IterableSubject, Iterable<?>> iterablesWithCustomDoubleToString() {
      return new Factory<IterableSubject, Iterable<?>>() {
        @Override
        public IterableSubject createSubject(FailureMetadata metadata, Iterable<?> actual) {
          return new IterableSubjectWithInheritedToString(metadata, actual);
        }
      };
    }