This example shows a pie chart of ozone AQI categories by the number of days each category occurred, with a legend listing each category and its corresponding day count. The chart is generated in React using D3 v5 APIs including `pie`, `arc`, `scaleOrdinal`, and `schemeCategory10` to create the slices, which are rendered as SVG paths. Data is loaded via `csv` from a GitHub gist and processed to count unique dates per category before being passed to the rendering function.