code: def join_to_the_boundary():
      """Send a stop signal to the boundary thread and join to it"""
      global the_boundary
      if the_boundary is not None:
          the_boundary.join()
          the_boundary = None
  
imports: import errno
  import json
  import logging
  import os
  import queue
  import sys
  import threading
  import uuid
  import numpy
  import zmq
  import cellprofiler_core.utilities.grid
  from cellprofiler_core.utilities.zmq._boundary import Boundary
  from cellprofiler_core.utilities.zmq.communicable.reply import LockStatusReply, Reply
  from cellprofiler_core.utilities.zmq.communicable.request import LockStatusRequest, Request
label_desc: Use image node_id 12 for calling a global function with example usage: join_to_the_boundary() without return types