get_strictness

Gets the known strictness of filters.

If the strictness is not known, gtk_filter_match_some is returned.

This value may change after emission of the [signal@Gtk.Filter:GtkFilter:changed] signal.

This function is meant purely for optimization purposes, filters can choose to omit implementing it, but `GtkFilterListModel` uses it.

Parameters:

this	a `GtkFilter`

Returns:

the strictness of this