According to http://www.sane-project.org/html/doc011.html
18.104.22.168 (Option Value Type), SANE_TYPE_GROUP: An option of this type
has no value. This type is used to group logically related options. A
group option is in effect up to the point where another group option
is encountered (or up to the end of the option list, if there are no
other group options). For group options, only members title and type
are valid in the option descriptor.
My understanding is that these groups indicate options that belong
together and are best shown together in the frontend UI.
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