A donut chart visualizes the total units purchased for each item in a dataset loaded from a CSV file. Each item's slice is labeled with its unit count, and a legend lists the items with color swatches and their corresponding values. The visualization is built with D3 v5, using the `d3.pie`, `d3.arc`, and `d3.scaleOrdinal` APIs to compute arc segments and assign colors, with SVG rendering for the chart and legend.