nautilus-image-copypaste is a Nautilus extension that allows users to set the clipboard from image files and to create image files from the clipboard. Reading the clipboard works, however I can't figure out how to set the clipboard at line 108.
The Python Gdk4 bindings do not have the set_texture method, which would have been the obvious choice.
The set method, which is available in the bindings, requires a GType (GDK_TYPE_TEXTURE), but I've been unable find that in the bindings.