code: def run(self, blocking=True):
          
          # localize variable access to minimize overhead
          # and to improve thread safety
          lock = self._lock
          q = self._queue
          delayfunc = self.delayfunc
          timefunc = self.timefunc
          pop = heapq.heappop
          while True:
              with lock:
                  if not q:
                      break
                  time, priority, action, argument, kwargs = q[0]
                  now = timefunc()
                  if time > now:
                      delay = True
                  else:
                      delay = False
                      pop(q)
              if delay:
                  if not blocking:
                      return time - now
                  delayfunc(time - now)
              else:
                  action(*argument, **kwargs)
                  delayfunc(0)
docs: Execute events until the queue is empty.
          If blocking is False executes the scheduled events due to
          expire soonest (if any) and then return the deadline of the
          next scheduled call in the scheduler.
  
          When there is a positive delay until the first event, the
          delay function is called and the event is left in the queue;
          otherwise, the event is removed from the queue and executed
          (its action function is called, passing it the argument).  If
          the delay function returns prematurely, it is simply
          restarted.
  
          It is legal for both the delay function and the action
          function to modify the queue or to raise an exception;
          exceptions are not caught but the scheduler's state remains
          well-defined so run() may be called again.
  
          A questionable hack is added to allow other threads to run:
          just after an event is executed, a delay of 0 is executed, to
          avoid monopolizing the CPU when other threads are also
          runnable.