SKSetAtFour

type SKSetAtFour<V extends [SK, SK, SK, SK]> = { 
  (prefix: V[0]): SetStorage<[V[1], V[2], V[3]]>; 
  (prefix: [V[0], V[1]]): SetStorage<[V[2], V[3]]>; 
  (prefix: [V[0], V[1], V[2]]): SetStorage<V[3]>; 
};