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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 horizontals(self):
 """ All horizontal squares from the piece's point of view. Returns a list of relative movements up to the board's bound. """

        horizontal_shifts = set(izip_longest(map(
            lambda i: i - self.x, range(self.board.length)), [], fillvalue=0))
        horizontal_shifts.discard((0, 0))
        return horizontal_shifts