src/vs/platform/actions/common/actions.ts/MenuId/constructor
class MenuId:	constructor(identifier: string) {
		if (MenuId._instances.has(identifier)) {
			throw new TypeError(`MenuId with identifier '${identifier}' already exists. Use MenuId.for(ident) or a unique identifier`);
		}
		MenuId._instances.set(identifier, this);
		this.id = identifier;
	}