This example visualizes monthly expenditures from a CSV file as a pie chart. The chart displays categories as colored slices, with each slice labeled by its associated data value, and includes a legend that maps the colors to their numeric values. The visualization is built using D3 version 5, specifically leveraging `d3.pie`, `d3.arc`, and `d3.scaleOrdinal` for the pie geometry, arc paths, and color mapping. Data is fetched asynchronously via `d3.csv` from a GitHub gist URL, and the SVG canvas is rendered with a fixed width and height.