This example demonstrates how to build a legend for bubble charts using SVG circles, dashed connector lines, and text labels. It shows three reference sizes (10, 50, and 100) positioned on a static canvas, with each label displaying placeholder text. The code uses d3.scaleSqrt() to map data values to pixel radii, then appends the legend elements via d3.selectAll().enter().append() in d3.v4. All rendering is done in a React-compatible HTML page, with the SVG object placed directly in the DOM.