Input animation to use in an [AnimationNodeBlendTree].
A resource to add to an [AnimationNodeBlendTree]. Only features one output set using the [member animation] property. Use it as an input for [AnimationNode] that blend animations together.
https://docs.godotengine.org/en/latest/tutorials/animation/animation_tree.html
Animation to use as an output. It is one of the animations provided by [member AnimationTree.anim_player].