# bpy.data.libraries.write not working?

I want to save selected objects into a separate .blend file in 2.8.

import bpy

filepath = "//new_library.blend"
data_blocks = set(bpy.context.selected_objects)
bpy.data.libraries.write(filepath, data_blocks)


I created a blank scene, added two spheres to it and saved everything. Afterwards I selected them both and let the script run through: A ".blend" file gets created, however it doesn't contain anything.

I re downloaded 2.79 and got the same result. So I am unsure where the problem lies and don't want to file a bug report immediately without having some outside input. Could somebody please clarify things for me, please?

Check the library files bpy.data.objects collection to confirm.