Compares two given items according to the sort order implemented
by the sorter.
Sorters implement a partial order:
* It is reflexive, ie a = a
* It is antisymmetric, ie if a < b and b < a, then a = b
* It is transitive, ie given any 3 items with a ≤ b and b ≤ c,
then a ≤ c
The sorter may signal it conforms to additional constraints
via the return value of [method@Gtk.Sorter.get_order].
Compares two given items according to the sort order implemented by the sorter.
Sorters implement a partial order:
* It is reflexive, ie a = a * It is antisymmetric, ie if a < b and b < a, then a = b * It is transitive, ie given any 3 items with a ≤ b and b ≤ c, then a ≤ c
The sorter may signal it conforms to additional constraints via the return value of [method@Gtk.Sorter.get_order].