* @return The value as a identifier.
*/
protected StyleIdentifier getArgumentAsIdentifier(
String functionName, List arguments, int index) {
StyleValue value = (StyleValue) arguments.get(index);
StyleIdentifier identifier = null;
if (value instanceof StyleIdentifier) {
identifier = (StyleIdentifier) value;
} else {
unexpectedType(functionName, index, StyleValueType.IDENTIFIER,
value);