This pie chart visualizes the distribution of diagnoses in a heart disease dataset sourced from a GitHub gist. The chart displays four categorical slices, each labeled with the diagnosis name, and uses a legend to map colors to the categories. Built with D3 v7, the code employs `d3.pie()` for arc generation, `d3.scaleOrdinal()` for color assignment, and `d3.select()` to build the SVG. It calculates counts from the CSV data using `d3.rollups` before rendering.