public function getMaximumLevels()
{
if ($this->maximumLevels === null) {
$this->maximumLevels = $this->tsValue('maximumLevels');
if ($this->maximumLevels > self::MAXIMUM_LEVELS_LIMIT) {
$this->maximumLevels = self::MAXIMUM_LEVELS_LIMIT;
}
}
return $this->maximumLevels;
}