def add_item_download_callback(callback):
session.item_download_callbacks.append(callback)<EOL>
Pass a function to be called when an item has finished downloading.
This can be used for performing notifications of download progress or
calling additional API functions.

:param callback: A function that takes four arguments. The first argument
    is the communicator object of the current pydas context, the second is
    the currently active API token and the third is the dict of item info,
    the fourth argument is the local download path of the item.
:type callback: (Communicator, string, dict, string) -> unknown