Checks if there are castling rights that are only possible in Chess960.

def has_chess960_castling_rights(self) -> bool:
        """
        Checks if there are castling rights that are only possible in Chess960.
        """
        # Get valid Chess960 castling rights.
        chess960 = self.chess960
        self.chess960 = True
        castling_rights = self.clean_castling_rights()
        self.chess960 = chess960

        # Standard chess castling rights can only be on the standard
        # starting rook squares.
        if castling_rights & ~BB_CORNERS:
            return True

        # If there are any castling rights in standard chess, the king must be
        # on e1 or e8.
        if castling_rights & BB_RANK_1 and not self.occupied_co[WHITE] & self.kings & BB_E1:
            return True
        if castling_rights & BB_RANK_8 and not self.occupied_co[BLACK] & self.kings & BB_E8:
            return True

        return False