This example visualizes the iris dataset, plotting sepal length against petal length and encoding species using different symbol shapes. It builds a scatter plot with D3 v7, using `d3.scaleLinear` for axes, `d3.scaleOrdinal` with `symbolsFill` to map species to shapes, and custom modules for axes and a shape legend. Data is fetched as CSV from a GitHub gist and parsed with `d3.csvParse`. The visualization is wrapped in a React-like state management pattern, though it renders directly into the DOM using `d3.select` and SVG elements.