Gemini Shortcut Discovery for Data Pipeline Optimization

Use Gemini 3's planning step #3 (Identify tools, shortcuts, or "power user" methods that solve the problem better than standard approaches) to optimize slow data processing code.

<context>{{PYTHON_ETL_SCRIPT}}</context> <task>Based on the script above, identify "power user" vectorization or memory-mapping methods that solve this aggregation task more efficiently than standard row loops, and provide the refactored code.</task>