Assume I am using iCloud Drive. Assume I have an external hard drive acting as my time machine drive attached to Mac 1. If I create a document on Mac 1 and save it to documents, I understand that the local version will be backed up to time machine. Then, if I modify the document on Mac 2, also using iCloud Drive and saved to documents on Mac 2, how is the modified document ever backed up to the time machine drive attached to Mac 1? Ideally, I would like to be able to work on my files on multiple Macs using the cloud and have everything current and backed up to time machine.