You can search for identifiers within the package.
in-package search v0.2.0
lablgtk3
GtkObject
val cast : 'a Gobject.obj -> [ `giu ] Gobject.obj
val _ref_sink : [> `giu ] Gobject.obj -> unit
val make : classe:string -> ([> `giu ] as 'a) Gobject.param list -> 'a Gobject.obj