This example visualizes the Iris flower dataset using a parallel coordinate plot, showing how four numeric attributes (sepal length, sepal width, petal length, petal width) relate across three species. Each species is color-coded via a custom `class_color` function, with semi-transparent polylines drawn as SVG paths. The code uses `d3.scalePoint` for the horizontal axis positions, `d3.scaleLinear` for each vertical dimension, and `d3.axisLeft` to render tick marks. Static axes are labeled, and the visualization renders with the d3.v5 library.