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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 score(self):
        'Return score from B perspective. If W is winning, score is negative.'
        working_board = np.copy(self.board)
        while EMPTY in working_board:
            unassigned_spaces = np.where(working_board == EMPTY)
            c = unassigned_spaces[0][0], unassigned_spaces[1][0]
            territory, borders = find_reached(working_board, c)
            border_colors = set(working_board[b] for b in borders)
            X_border = BLACK in border_colors
            O_border = WHITE in border_colors
            if X_border and not O_border:
                territory_color = BLACK
            elif O_border and not X_border:
                territory_color = WHITE
            else:
                territory_color = UNKNOWN  # dame, or seki
            place_stones(working_board, territory_color, territory)

        return np.count_nonzero(working_board == BLACK) - np.count_nonzero(working_board == WHITE) - self.komi