public static int GetFrameLengthFromAnimationGroup(
this Sequence sequence, int animationGroupIndex) =>
sequence.AggregateAnimationGroup <int>(animationGroupIndex, (x, i) =>
Math.Max(x, sequence.GetFrameLengthFromAnimation(i)));
public static Rectangle GetVisibilityRectangleFromAnimationGroup(
this Sequence sequence, int animationGroupIndex) =>
sequence.AggregateAnimationGroup <Rectangle>(animationGroupIndex, (x, i) =>
x.Union(sequence.GetVisibilityRectangleFromAnimation(i)));
