extensions/markdown-language-features/src/languageFeatures/documentSymbols.ts/MdDocumentSymbolProvider/provideDocumentSymbols
class MdDocumentSymbolProvider:	public async provideDocumentSymbols(document: ITextDocument): Promise<vscode.DocumentSymbol[]> {
		const toc = await this.tocProvider.getForDocument(document);
		const root: MarkdownSymbol = {
			level: -Infinity,
			children: [],
			parent: undefined
		};
		this.buildTree(root, toc.entries);
		return root.children;
	}