@classmethod
def make_symmetric(cls, mat):
    """
        Make a matrix symmetric, by averaging with its transpose.

        Parameters
        ----------
        mat : array-like, shape=[n_samples, n, n]

        Returns
        -------
        sym : array-like, shape=[n_samples, n, n]
        """
    return 1 / 2 * (mat + cls.transpose(mat))
