How to register the snippetKeymap ?

Most exported keymaps in core packages have a type readonly KeyBinding[] which can be used in keymap.of().
However, snippetKeymap in @codemirror/autocomplete has the type Facet<readonly KeyBinding[], readonly KeyBinding[]>. How is the snippetKeymap meant to be used ? I haven’t found any examples using it (or using snippets for that matter) and the reference manual is not clear about how to use it either.

How is this expected to be used ?

This is not a keymap, but a way to replace the default keybindings associated with snippets. But its docs already tell you this.