overlaps lists the following options for multiple:

`multiple: Literal["first", "all", "last", "contained"] = "all",`

https://github.com/pyranges/ruranges/blob/master/ruranges/__init__.py#L83C5-L83C68

But it seems to me the only "first", "all", "last" are supported.

Also the wording of the help is confusing:

    The four mandatory arrays (starts, ends, starts2, ends2) must all have the same length.
    If one of groups or groups2 is provided, then both must be provided and have the same length
    as the other arrays.

Should it not be that starts, ends (and groups if provided) should have the same length and starts2, ends2 (and groups2 if provided)?