<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def cmd_move(db=None):
 """Rename a database within a server. When used with --force, an existing database with the same name as DEST is replaced, the original is renamed out of place in the form DEST_old_YYYYMMDD (unless --no-backup is specified). """

    if db is None:
        db = connect()

    pg_move_extended(db, args.src, args.dest)