public function classNameForEvent($event): string
    {
        if ( ! isset($this->eventClasses[$event])) {
            throw new \InvalidArgumentException("Could not find a class for the event {$event}.");
        }
        return $this->eventClasses[$event];
    }
public function classNameForEvent($event): string
    {
        if ( ! isset($this->eventClasses[$event])) {
            throw new \InvalidArgumentException("Could not find a class for the event {$event}.");
        }
        return $this->eventClasses[$event];
    }
public function classNameForEvent ( $ event ) : string { if ( ! isset ( $ this -> eventClasses [ $ event ] ) ) { throw new \ InvalidArgumentException ( "Could not find a class for the event {$event}." ) ; } return $ this -> eventClasses [ $ event ] ; }
retrieve the fully qualified class name for an 'event name'

@param $event
@return string
retrieve the fully qualified class name for an event name