code: def combining_search(self):
          
          start = (
              self.get_pair(), 
              (
                  self.cube["L"], 
                  self.cube["U"], 
                  self.cube["F"], 
                  self.cube["D"], 
                  self.cube["R"], 
                  self.cube["B"], 
                  ), 
              )
          return sum(path_actions(a_star_search(start, 
                         self.combining_successors, 
                         lambda x: len(x), 
                         self.combining_goal)), Formula())
docs: Searching the path for combining the pair.