Sessions did that already -- in early 2017. It's customary when a new President is elected.
Interestingly, President Trump refused to accept one resignation -- that of a guy who was then the U.S. Attorney for the District of Maryland: Rod Rosenstein.
15 posted on 11/08/2018 3:35:23 PM PST by Alberta's Child
("The Russians escaped while we weren't watching them ... like Russians will.")