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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 evecsCV(self):
 """ The eigenvectors of the principal directions of the mu space. This is a Dictionary of numpy.matrix Each entry in the dictionary is as described under evals. Each numpy.matrix contains the eigenvectors which, with the eigenvalues in evals, are needed to rotate the coordinate system to one in which the metric is the identity matrix. """

        if self._evecsCV is None:
            errMsg = "The covariance eigenvectors have not been set in the "
            errMsg += "metricParameters instance."
            raise ValueError(errMsg)
        return self._evecsCV