docs: public Class<? extends AbstractInvokable> getInvokableClass(ClassLoader cl) {
  		if (cl == null) {
  			throw new NullPointerException("The classloader must not be null.");
  		}
  		if (invokableClassName == null) {
  			return null;
  		}
  
  		try {
  			return Class.forName(invokableClassName, true, cl).asSubclass(AbstractInvokable.class);
  		}
  		catch (ClassNotFoundException e) {
  			throw new RuntimeException("The user-code class could not be resolved.", e);
  		}
  		catch (ClassCastException e) {
  			throw new RuntimeException("The user-code class is no subclass of " + AbstractInvokable.class.getName(), e);
  		}
  	}