public List<Namespace> getAdditionalNamespaces() {
    // Not having the returned list be live allows us to avoid creating a
    // new list object when XMLOutputter calls this method on an element
    // with an empty list.
    if (additionalNamespaces == null) {
      return Collections.emptyList();
    }
    return Collections.unmodifiableList(additionalNamespaces);
  }
public List<Namespace> getAdditionalNamespaces()