protected function addToList($listMapping, $property, $value) {
if ($this->debug) {
print "Adding to list: {$property} -> " . $value['type'] . ':' . $value['value'] . "\n";
}
// Create property in the list mapping if it doesn't already exist
if (!isset($listMapping->{$property})) {
$listMapping->{$property} = array();
}
array_push($listMapping->{$property}, $value);
}