Kerr rotation as solitonic whirl around the Schwarzschild black hole

We propose the new derivation of the Kerr solution by adding to the Schwarzchild black hole the solitonic vortex made from the pure gravitational field. With this method, we can figure out how rotational energy can contribute to the mass of the resulting Kerr black hole. This suggests a new mode to think on the relation between the mass and angular momentum of a Kerr black hole.