This example shows a small network of six named nodes connected by weighted links, displayed as an SVG force-directed graph. The visualization uses D3 v4 with the legacy `d3.layout.force` API to simulate physical forces that position nodes and draw straight lines between them. Node labels and circles are rendered via SVG groups, with link stroke widths scaled by the square root of the link weight, and the data is loaded from a local `data.json` file.