static withEffect(arg, duration) {
		const result = Array.isArray(arg) ? arg : [ arg ];

		if(duration) {
			if(duration.ms > 0) {
				result.push(DEFAULT_EFFECT);
				result.push(duration.ms);
			} else {
				result.push('sudden');
				result.push(0);
			}
		} else {
			result.push(DEFAULT_EFFECT);
			result.push(DEFAULT_DURATION);
		}

		return result;
	}
Helper method to combine an argument with effect information.