src/vs/workbench/contrib/typeHierarchy/common/typeHierarchy.ts/TypeHierarchyModel/constructor
class TypeHierarchyModel:	private constructor(
		readonly id: string,
		readonly provider: TypeHierarchyProvider,
		readonly roots: TypeHierarchyItem[],
		readonly ref: RefCountedDisposable,
	) {
		this.root = roots[0];
	}