This example displays a hierarchical tree diagram illustrating sleep data for three people, with leaf nodes representing specific attributes like sleep duration, stress level, and productivity. The root node, "Sleep Data," branches to person nodes, which then branch to their respective attributes. The visualization is rendered as an SVG using D3 v7, employing the `d3.hierarchy` and `d3.tree` layout functions to position nodes and `d3.linkVertical` to draw connecting paths. Node colors vary by depth: blue for the root, yellow for person nodes, and red for attribute leaves.