Deoldify Vapoursynth filter

[Selur]

I do not understand ref_freq.

ref_freq: int = None,
...
    :param ref_freq:            If (ref_merge > 0 or method == 5). If > 0 will be generated at least a reference frame
                                every "ref_freq" frames. range [0-1500]. If is not set, is assigned automatically a
                                value depending on ref_merge value and method.

I interpret this as that:
1. it should only be used if ref_merge > 0 or method == 5.
2. If it is set to 'None' depending on ref_merge value and method some automatic value is assigned.
3. If set to a value > 0 at least a reference frame every "ref_freq" frames will be generated (1-1500).
If set to 0 ???
Is there a difference between None and 0?
If there is no difference, then 'None' should not be used at all.
If there is a difference, please explain it.

Cu Selur

Ps.: updated Hybrid_deoldify to include 'Deep-Remaster' as ex_method. (did not add ref_freq since I don't get it)