def _populate_unknown_statuses(set_tasks):
 visited = set()
 for task in set_tasks['still_pending_not_ext']:
  _depth_first_search(set_tasks, task, visited)

def _populate_unknown_statuses ( set_tasks ) : visited = set ( ) for task in set_tasks [ 'still_pending_not_ext' ] : _depth_first_search ( set_tasks , task , visited )
add the "upstream_*" and "not_run" statuses my mutating set_tasks .