code: String getNamespaceAliasForUriErrorOnUnknown(String namespaceUri) {
      String result = getAliasForUri(namespaceUri);
      Preconditions.checkArgument(
          result != null,
          "invalid XML: no alias declared for namesapce <%s>; "
              + "work-around by setting XML namepace directly by calling the set method of %s",
          namespaceUri,
          XmlNamespaceDictionary.class.getName());
      return result;
    }
docs: Returns the namespace alias to use for a given namespace URI, throwing an exception if the
  namespace URI can be found in this dictionary.
  
  @param namespaceUri namespace URI
  @throws IllegalArgumentException if the namespace URI is not found in this dictionary