Tutorial improvements

[Nicolaidavies]

Changes

This PR improves the tutorial by:

• adding an assertion to tutorial 3. Without this assertion, there is no check of the newly implemented functionality.
• removing unused arguments that would otherwise stop the code from compiling.
• including code that is relevant for step 4, that would stop the code from compiling at that point in the tutorial.

I made all the changes while following the tutorial.

[Aaronontheweb]

Thanks @Nicolaidavies - looks like there's something DocFx isn't happy about in the build logs. I'll check it out today - it's usually something small. We appreciate your contribution!

[Aaronontheweb]

Actually, looks like it wasn't even a DocFx validation issue - NuGet 503'd during a package restore. I'll just re-run those steps.

[Nicolaidavies]

Thank you @Aaronontheweb !