def make_exp_kernel(L0):

    def exp_kernel(x1, x2):
        x1 = np.expand_dims(x1, 2)
        x2 = x2.T
        return np.exp(((- np.mean(np.abs((x1 - x2)), axis=1)) / L0))
    return exp_kernel
def make_exp_kernel(L0):

    def exp_kernel(x1, x2):
        x1 = np.expand_dims(x1, 2)
        x2 = x2.T
        return np.exp(((- np.mean(np.abs((x1 - x2)), axis=1)) / L0))
    return exp_kernel