public void start(ASTargument node) throws HaltTraversalException {
final Object value = node.getValue();
if (value == null) {
LOG.debug("Ignoring null argument");
} else if (value instanceof NumberArgument) {
final NumberArgument numberArgument = (NumberArgument) value;
Integer integer = numberArgument.getInteger();
if (integer == null) {
LOG.debug("Ignoring null numeric argument");
} else {
final int number = integer.intValue();
handler.argument(number);