src/vs/editor/common/languages/supports/languageBracketsConfiguration.ts/LazyMap/get
class LazyMap:	public get(key: TKey): TValue {
		if (this._map.has(key)) {
			return this._map.get(key)!;
		}
		const value = this.initialize(key);
		this._map.set(key, value);
		return value;
	}