extensions/markdown-language-features/src/tableOfContentsProvider.ts/TableOfContentsProvider/getToc
class TableOfContentsProvider:	public async getToc(): Promise<TocEntry[]> {
		if (!this.toc) {
			try {
				this.toc = await this.buildToc(this.document);
			} catch (e) {
				this.toc = [];
			}
		}
		return this.toc;
	}