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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 value(self):

 """Compute option value according to BSM model."""

        return self._sign[1] * self.S0 * norm.cdf(
            self._sign[1] * self.d1, 0.0, 1.0
        ) - self._sign[1] * self.K * np.exp(-self.r * self.T) * norm.cdf(
            self._sign[1] * self.d2, 0.0, 1.0
        )