src/vs/editor/common/services/languagesRegistry.ts/LanguagesRegistry/getLanguageIdByMimeType
class LanguagesRegistry:	public getLanguageIdByMimeType(mimeType: string | null | undefined): string | null {
		if (!mimeType) {
			return null;
		}
		if (hasOwnProperty.call(this._mimeTypesMap, mimeType)) {
			return this._mimeTypesMap[mimeType];
		}
		return null;
	}