Streams Training Topic

I'm interested in seeing an example that shows us why the imperative is unsafe and how streams solve that.

Start by reviewing the repository's existing training material and examples to find where a Streams topic belongs. The issue names no file or test, so identify the appropriate entry point and define an example that contrasts unsafe imperative code with a streams-based solution; done means the new training material clearly demonstrates that difference.

Written by the indexing model from the issue text.