public AnimLayer getLayer(String layerName) {
        AnimLayer result = layers.get(layerName);
        if (result == null) {
            throw new IllegalArgumentException("Unknown layer " + layerName);
        }
        return result;
    }
Provides access to the named layer.

@param layerName the name of the layer to access
@return the pre-existing instance
jme3-core/src/main/java/com/jme3/anim/AnimComposer.java