class_docstr: Schedules the given callback to be called once.
  
  The callback is called once, after callback_time milliseconds.
  
  `start` must be called after the DelayedCallback is created.
  
  The timeout is calculated from when `start` is called.
class_docstr_tok: ["Schedules","the","given","callback","to","be","called","once",".","The","callback","is","called","once",",","after","callback_time","milliseconds",".","`","start","`","must","be","called","after","the","DelayedCallback","is","created",".","The","timeout","is","calculated","from","when","`","start","`","is","called","."]
docstr: Starts the timer.
docstr_tok: ["Starts","the","timer","."]
code: def start(self):
      """Starts the timer."""
      self._running = True
      self._firstrun = True
      self._next_timeout = time.time() + self.callback_time / 1000.0
      self.io_loop.add_timeout(self._next_timeout, self._run)
  
imports: import time
  import warnings
  from typing import Tuple
  from zmq import ETERM, POLLERR, POLLIN, POLLOUT, Poller, ZMQError
  from .minitornado.ioloop import PeriodicCallback, PollIOLoop
  from .minitornado.log import gen_log
label_desc: Use image node_id 2 for calling the DelayedCallback obj's underlying member method code with example usage: obj.start() without return types