var  SoftwareHouse = (function() {

function implement(obj, method) {
	return (obj && obj[method] && obj[method] instanceof Function);
}

return class {
	constructor() {
		this.employees = [];
	}

	hire(dev) {
		if (implement(dev, "writeCode")) {
			this.employees.push(dev);
			} else {
				throw new Error("Argument nie implementuje metody writeCode.")
			}
		}
	};
})();