copy method
recursive -- If set to true, descendants of the object are copied next to the existing ones.
If set to false, descendants are left unchanged. Default is true.
Copies the given object into this object. Note: Event listeners and user-defined callbacks (onAfterRender and onBeforeRender) are not copied.
Implementation
@override
MorphAnimMesh copy(Object3D source, [bool? recursive ]) {
super.copy( source, recursive );
mixer = AnimationMixer( this );
return this;
}