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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 _compute_error(self):
 """ Evaluate the absolute error of the Nystroem approximation for each column """

        # err_i = sum_j R_{k,ij} A_{k,ji} - d_i
        self._err = np.sum(np.multiply(self._R_k, self._C_k.T), axis=0) - self._d