Added a bit of clarification of how important classes attribute is to the tool doc

[Tobychev]

Besides added a minimal bit of clarification of how important classes attribute is to the tool doc, I also did some other changes to the example notebook:

• I enabled scrolling to some of the cells so the full environment dumps don't swamp the useful content in the example
• I added a docstring to SecondaryMyComponent, which means a later example doesn't result in a distracting error

[review-notebook-app]

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[maxnoe]

@Tobychev This PR contains also your benchmarks code. Probably because you started from that branch and not from master. To make sure you start a fresh branch from master for a new PR, you can do:

$ git fetch # get latest github changes
$ git switch -c <new branch name> origin/master  # start <new branch> from the current master

To fix it here, you can do git rebase -i origin/master and "drop" all commits that don't belong here and then git push -f

[maxnoe]

Ah, and also please "strip out" the notebook, e.g. Cell → All Output → Clear and Save.

[maxnoe]

The actual changes to the docs and the Tool tutorial look good!

[maxnoe]

Thanks! Looks good now.