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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 board(self):
 """Calculates board from flop, turn and river."""

        board = []
        if self.flop:
            board.extend(self.flop.cards)
            if self.turn:
                board.append(self.turn)
                if self.river:
                    board.append(self.river)
        return tuple(board) if board else None