Modifications on notebooks and hands on in part 3

This MR was first proposed as !78 (closed) but was closed as there were few improvements to perform in hands on and depending on a master without #114 (closed) was a pain.

added 1 commit

• a2b1ddb4 - Indent.

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assigned to @sgilles

added 3 commits

• bcc99b6b - Add the assert in Unused() method.
• 484e67fd - HandsOn: remove the 'clever' post-increment of array index, to be in agreement...
• 99f89386 - Add a comment about assert.

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added 1 commit

• 82a58c9e - Typo.

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resolved all threads

approved this merge request

mentioned in commit d1dd1208

merged