docstr: initialize the ioloop event handler
docstr_tok: ["initialize","the","ioloop","event","handler"]
code: def _init_io_state(self):
      """initialize the ioloop event handler"""
      self.io_loop.add_handler(
          self._shadow_sock, self._handle_events, self._READ
      )
      self._call_later(0, self._handle_events)
  
imports: from collections import namedtuple, deque
  from itertools import chain
  from zmq import EVENTS, POLLOUT, POLLIN
  import zmq
label_desc: Use image node_id 23 for calling the _AsyncSocket obj's underlying member method code with example usage: obj._init_io_state() without return types