class_docstr: A basic logging handler that emits log messages through a PUB socket.
  
  Takes a PUB socket already bound to interfaces or an interface to bind to.
  
  Example::
  
      sock = context.socket(zmq.PUB)
      sock.bind('inproc://log')
      handler = PUBHandler(sock)
  
  Or::
  
      handler = PUBHandler('inproc://loc')
  
  These are equivalent.
  
  Log messages handled by this handler are broadcast with ZMQ topics
  ``this.root_topic`` comes first, followed by the log level
  (DEBUG,INFO,etc.), followed by any additional subtopics specified in the
  message by: log.debug("subtopic.subsub::the real message")
code: def root_topic(self):
      return self._root_topic
  
file_path: catboost/contrib/python/pyzmq/py2/zmq/log/handlers.py
imports: import logging
  from logging import INFO, DEBUG, WARN, ERROR, FATAL
  import zmq
  from zmq.utils.strtypes import bytes, unicode, cast_bytes
label_desc: Use image node_id 2 for calling the PUBHandler obj's underlying member method code with example usage: obj.root_topic() and returns: self