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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def feed(self, cube, pair):
 """ Feed Cube to the solver. """

        self.cube = cube
        if pair not in ["FR", "RB", "BL", "LF"]:
            pair = ["FR", "RB", "BL", "LF"][["RF", "BR", "LB", "FL"].index(pair)]
        self.pair = pair