Update introduction.md to dict methods views examples

Programming Python
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keys(), values(), items() can be recalculated. Assigning to a variable beforehand makes the dynamic attribute of the views clear.
This is my first contribution and very first pull request.

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Hi @oezg :wave:

Thank you for taking the time to submit a PR. Unfortunately, I think assigning a variable to palette_I.keys() confuses things here. Especially with the section that follows.

I would rather leave the introduction as it stands for now, and maybe revisit it down the road if it appears to be confusing students.

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Hi Bethany,
Thank you for responding so quickly.