class_docstr: The heartbeat channel which monitors the kernel heartbeat.
  
  Note that the heartbeat channel is paused by default. As long as you start
  this channel, the kernel manager will ensure that it is paused and un-paused
  as appropriate.
class_docstr_tok: ["The","heartbeat","channel","which","monitors","the","kernel","heartbeat",".","Note","that","the","heartbeat","channel","is","paused","by","default",".","As","long","as","you","start","this","channel",",","the","kernel","manager","will","ensure","that","it","is","paused","and","un-paused","as","appropriate","."]
docstr: This method is called in the ioloop thread when a message arrives.
  
  Subclasses should override this method to handle incoming messages.
  It is important to remember that this method is called in the thread
  so that some logic must be done to ensure that the application level
  handlers are called in the application thread.
docstr_tok: ["This","method","is","called","in","the","ioloop","thread","when","a","message","arrives",".","Subclasses","should","override","this","method","to","handle","incoming","messages",".","It","is","important","to","remember","that","this","method","is","called","in","the","thread","so","that","some","logic","must","be","done","to","ensure","that","the","application","level","handlers","are","called","in","the","application","thread","."]
code: def call_handlers(self, since_last_heartbeat):
      """This method is called in the ioloop thread when a message arrives.
  
      Subclasses should override this method to handle incoming messages.
      It is important to remember that this method is called in the thread
      so that some logic must be done to ensure that the application level
      handlers are called in the application thread.
      """
      pass
  
imports: from __future__ import absolute_import
  import atexit
  import errno
  from threading import Thread, Event
  import time
  import zmq
  from zmq import ZMQError
  from jupyter_client import protocol_version_info
  from .channelsabc import HBChannelABC
label_desc: Use image node_id 11 for calling the HBChannel obj's underlying member method code with example usage: obj.call_handlers(since_last_heartbeat) without return types