Inverse of posterior covariance

def precision(self):
        """
        Inverse of posterior covariance
        """
        if self._precision is None:
            cov = np.atleast_3d(self.covariance)
            self._precision = np.zeros(cov.shape)  # if one covariance per dimension
            for p in range(cov.shape[-1]):
                self._precision[:, :, p] = pdinv(cov[:, :, p])[0]
        return self._precision