docs: def wait(self, timeout=None):
          """
          An implementation of the wait method which doesn't involve
          polling but instead utilizes a "real" synchronization
          scheme.
          """
          import threading
  
          if self._state!=self.PENDING:
              return
  
          e = threading.Event()
          self.addCallback(lambda v: e.set())
          self.addErrback(lambda r: e.set())
          e.wait(timeout)