Returns the Gram Matrix

        Parameters
        ----------
        parm : np.ndarray
            Parameters for the Gram Matrix

        Returns
        ----------
        - Gram Matrix (np.ndarray)

def K(self, parm):
        """ Returns the Gram Matrix

        Parameters
        ----------
        parm : np.ndarray
            Parameters for the Gram Matrix

        Returns
        ----------
        - Gram Matrix (np.ndarray)
        """
        return ARD_K_matrix(self.X, parm) + np.identity(self.X.shape[0])*(10**-10)