@classmethod
  def wait_all(cls, futures):
    # TODO: Flatten MultiRpcs.
    waiting_on = set(futures)
    ev = eventloop.get_event_loop()
    while waiting_on:
      waiting_on = set(f for f in waiting_on if f.state not in cls.RUNNING)
      ev.run1()
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/ext/ndb/tasklets.py/Future.wait_all/operator `==` -> `not in`