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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 evecs(self):
 """ The eigenvectors of the parameter 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._evecs is None:
            errMsg = "The metric eigenvectors have not been set in the "
            errMsg += "metricParameters instance."
            raise ValueError(errMsg)
        return self._evecs