AutoInjector | allow auto inject instances for Zenject package | Editor library

So I'm following through some code snippets for AutoInjector and Automapper online, and noticed something that I don't really understand.

In the code, AutoInjector is Registering Automapper for use in this line.

container.Register(() => config.CreateMapper(container.GetInstance));

I noticed that container.GetInstance isn't having anything passed into it.

After some tinkering, I tried to do var instance = container.GetInstance(); in a console app, but it gives the error The type arguments for method 'Container.GetInstance() cannot be inferred from the usage. Try specifying the type arguments explicitly.

Obviously, the arguments being passed are inferred from the outer method config.CreateMapper()

I was wondering if there was a way to step through the code so I can see what is being passed into container.GetInstance(). When I step through the code, it just steps over the line and doesn't show me what's being passed into the method.