src/vs/workbench/services/textMate/browser/abstractTextMateService.ts/AbstractTextMateService/createGrammar
class AbstractTextMateService:	public async createGrammar(modeId: string): Promise<IGrammar | null> {
		const languageId = this._modeService.getLanguageIdentifier(modeId);
		if (!languageId) {
			return null;
		}
		const grammarFactory = await this._getOrCreateGrammarFactory();
		if (!grammarFactory.has(languageId.id)) {
			return null;
		}
		const { grammar } = await grammarFactory.createGrammar(languageId.id);
		return grammar;
	}