<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def solve(self):
 """ Solve the OLL. Returns an Formula. """

        if not isinstance(self.cube, Cube):
            raise ValueError("Use Solver.feed(cube) to feed the cube to solver.")
        self.recognise()
        self.cube(algo_dict[self.case])
        return algo_dict[self.case]