public Unit<TUnit> GetCurrent<TResource, TUnit>()
            where TResource : Resource<TUnit>
            where TUnit : IUnit {
            if (!ResourceCounter.TryGetValue(typeof(TResource), out var resourceContext)) {
                resourceContext = new ResourceContext<TUnit>();
                ResourceCounter.Add(typeof(TResource), resourceContext);
            }
            return ((ResourceContext<TUnit>)resourceContext).Current;
        }