Laravel 5.5 - 从API Resource类中,如何获取底层模型类名?

I have a Laravel 5.5 app with an API resource class. How do I get the underlying model class name from within the toArray() method? I'm aware that you can access the properties and methods of the underlying model using $this-> because the class will automatically proxy it to the underlying model. But how do I actually retrieve either the underlying model itself, or more importantly, the model class name? Is there a way?

If you look at the constructor of the Resource class, you'll see the instance is loaded into a $resource property.

get_class($this->resource);