@Override
    public void setMask(AnimationMask mask) {
        super.setMask(mask);

        if (maskPropagationEnabled) {
            for (Action action : actions) {
                action.setMask(mask);
            }
        }
    }
Sets the animation mask which determines which part of the model will 
be animated by the animation layer. If the {@link BaseAction#isMaskPropagationEnabled()} is false, setting
the mask attribute will not affect the actions under this base action. Setting this to 'null' will animate
the entire model.

@param mask an animation mask to be applied to this action (nullable).
@see com.jme3.anim.AnimLayer to adjust the animation mask to control which part will be animated
@see BaseAction#setMaskPropagationEnabled(boolean)
jme3-core/src/main/java/com/jme3/anim/tween/action/BaseAction.java