class ExtraFieldPropagation implements Propagation<K> {

  @Deprecated @Nullable public static String get(String name) {
    BaggageField field = BaggageField.getByName(validateFieldName(name));
    if (field == null) return null;
    return field.getValue();
  }

    ExtraFieldPropagation(Propagation<K> delegate, List<K> extraKeys);

}