This tree map visualizes the average passenger count (APC) for airlines departing from San Francisco International Airport, using data from `sfo_data.csv`. It displays each airline as a colored rectangle sized proportionally to its APC value, with the airline’s IATA code (e.g., UA, AS) labeled inside its cell. The visualization is built with D3 v4, using the `d3.stratify` and `d3.treemap` APIs to compute the hierarchical layout and render the rectangles as SVG elements, with all values sourced directly from the CSV file.