code: def initialize(cls, url_prefix="", port=None, address=None):
      if cls.initialized:
          return
  
      # Create the class instance
      app = cls(url_prefix=url_prefix)
  
      cls.url_prefix = url_prefix
  
      # This port selection algorithm is borrowed, more or less
      # verbatim, from IPython.
      def random_ports(port, n):
          """
          Generate a list of n random ports near the given port.
  
          The first 5 ports will be sequential, and the remaining n-5 will be
          randomly selected in the range [port-2*n, port+2*n].
          """
          for i in range(min(5, n)):
              yield port + i
          for i in range(n - 5):
              yield port + random.randint(-2 * n, 2 * n)
  
      success = None
  
      if address is None:
          cls.address = rcParams["webagg.address"]
      else:
          cls.address = address
      cls.port = rcParams["webagg.port"]
      for port in random_ports(
          cls.port, rcParams["webagg.port_retries"]
      ):
          try:
              app.listen(port, cls.address)
          except socket.error as e:
              if e.errno != errno.EADDRINUSE:
                  raise
          else:
              cls.port = port
              success = True
              break
  
      if not success:
          raise SystemExit(
              "The webagg server could not be started because an available "
              "port could not be found"
          )
  
      cls.initialized = True
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  from contextlib import contextmanager
  import errno
  import json
  import os
  import random
  import sys
  import signal
  import socket
  import threading
  import tornado.web
  import tornado.ioloop
  import tornado.websocket
  from matplotlib import rcParams
  from matplotlib.backend_bases import _Backend
  from matplotlib._pylab_helpers import Gcf
  from .None import backend_webagg_core
  from .backend_webagg_core import TimerTornado
label_desc: Use image node_id 2 for calling the WebAggApplication obj's underlying member method code with example usage: obj.initialize(cls, url_prefix, port, address) without return types