def plot_input(ace_model, fname='ace_input.png'):
    """Plot the transforms."""
    if not plt:
        raise ImportError('Cannot plot without the matplotlib package')
    plt.rcParams.update({'font.size': 8})
    plt.figure()
    num_cols = len(ace_model.x) / 2 + 1
    for i in range(len(ace_model.x)):
        plt.subplot(num_cols, 2, i + 1)
        plt.plot(ace_model.x[i], ace_model.y, '.')
        plt.xlabel('x{0}'.format(i))
        plt.ylabel('y')

    plt.tight_layout()

    if fname:
        plt.savefig(fname)
    else:
        plt.show()