class py_solution:  
    def sub_sets(self, sset):  
        return self.subsetsRecur([], sorted(sset))  
      
    def subsetsRecur(self, current, sset):  
        if sset:  
            return self.subsetsRecur(current, sset[1:]) + self.subsetsRecur(current + [sset[0]], sset[1:])  
        return [current]  
  
print(py_solution().sub_sets([4,5,6]))