Sam Thursfield authored Sep 25, 2017 and Rico Tzschichholz committed Sep 27, 2017

The GtkFlowBoxCreateWidgetFunc type lacked GObject Introspection
annotations for its arguments. This made gtk_flow_box_bind_model()
unusable from Python as the callback function would be passed useless
values.

The annotations that I've added match those of the similar callback
type GtkListBoxCreateWidgetFunc.

https://bugzilla.gnome.org/show_bug.cgi?id=780758