private function getHandler($class, $optionName)
{
if (isset(FormatterLoader::$extraOptionHandlers[$class][$optionName])) {
// Get the closure
$closure = FormatterLoader::$extraOptionHandlers[$class][$optionName];
$this->assertTrue(is_callable($closure));
return $closure;
} else {
throw new \Exception(sprintf('Handler %s is not defined for class %s', $optionName, $class));
}
}