Custom GraphInstance Mixed Layout
This example replaces the default relation-graph core with a custom `RelationGraphCore` subclass that reads two inline datasets from `graphOptions.data` and composes them into one center-plus-tree scene. It is a focused reference for provider-level graph-core injection, custom `doLayout()` orchestration, and one-canvas mixed-layout composition.
Use a Custom GraphInstance to Load Data and Compose Two Layouts
What This Example Builds
This example builds a viewer-style relation-graph scene that renders two disconnected datasets inside one full-height canvas. The left side appears as a centered cluster of smaller circular nodes with straight links, while the right side appears as a left-to-right tree with wider rectangular nodes and curved labeled edges.
Users do not edit graph content directly. They inspect the prepared scene, u