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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 evaluate_policy(self, sigma):
 """ Compute the value of a policy. Parameters sigma : array_like(int, ndim=1) Policy vector, of length n. Returns ------- v_sigma : ndarray(float, ndim=1) Value vector of `sigma`, of length n. """

        if self.beta == 1:
            raise NotImplementedError(self._error_msg_no_discounting)

        # Solve (I - beta * Q_sigma) v = R_sigma for v
        R_sigma, Q_sigma = self.RQ_sigma(sigma)
        b = R_sigma

        A = self._I - self.beta * Q_sigma

        v_sigma = self._lineq_solve(A, b)

        return v_sigma