code: def get_pair(self):
          
          colours = (
              self.cube[self.pair[0]].colour, 
              self.cube[self.pair[1]].colour, 
              self.cube["D"].colour
              )
          result_corner = self.cube.children.copy()
          for c in colours[:2]:
              result_corner &= self.cube.has_colour(c)
          result_edge = result_corner & self.cube.select_type("edge")
          result_corner &= self.cube.has_colour(colours[2])
          return (list(result_corner)[0], list(result_edge)[0])
docs: Get the F2L pair (corner, edge).