src/vs/workbench/contrib/audioCues/browser/audioCueService.ts/Cache/get
class Cache:	public get(arg: TArg): TValue {
		if (this.map.has(arg)) {
			return this.map.get(arg)!;
		}

		const value = this.getValue(arg);
		this.map.set(arg, value);
		return value;
	}