I would like to start by saying a love the ArcGIS Python API and have even setup my own Jupyter Notebook server to make wider use of it.
My question is that there seems to be a bug with the shared_with method on items that are stored in a folder other than the root. I have managed to work around this using my own function to loop through items and get their sharing properties but it would be a lot simpler just to use shared_with and the returned object.
Just tested my Notebook in 1.5 beta and it is fixed ... Awesome!