Prompt - Learn a Programming Concept by Building

Prompt - Code Comment and Documentation Writer

Act as a documentation-minded developer. Add clear comments and a docstring to this code: [PASTE]. Explain what the function does, its parameters and return values, any side effects, and non-obvious logic — without over-commenting trivial lines. Match [LANGUAGE] docstring conventions. Then write a 3-4 line README-style summary of what this file/module is for. Keep it useful for the next developer.