Levels thing

def LevelsM(clip, points, levels, xpass=[0, 'peak'], return_expr=False):
    qm = len(points)
    peak = [(1 << clip.format.bits_per_sample) - 1, 1][clip.format.sample_type]

    if len(set(xpass)) == 1:
        expr = f'x {points[0]} < x {points[-1]} > or {xpass[0]} '
        qm -= 1
    else:
        expr = f'x {points[0]} < {xpass[0]} x {points[-1]} > {xpass[-1]} '

    for x in range(len(points) - 1):
        if points[x+1] < points[-1]:
            expr += f' x {points[x+1]} <= '
        if levels[x] == levels[x+1]:
            expr += f' {peak * levels[x]} '
        else:
            expr += f' x {points[x]} - {peak * (levels[x+1] - levels[x])/(points[x+1] - points[x])} * {peak * levels[x]} + '

    for _ in range(qm):
        expr += ' ? '

    expr = expr.replace('  ', ' ').replace('peak', f'{peak}')

    if return_expr:
        return expr

    return clip.std.Expr(expr)