docstr: Clear up any closed Comms.
code: def clearup_closed(self):
      """Clear up any closed Comms."""
      self.web_sockets = {
          socket for socket in self.web_sockets if socket.is_open()
      }
  
      if len(self.web_sockets) == 0:
          CloseEvent("close_event", self.canvas)._process()
  
imports: from base64 import b64encode
  import io
  import json
  import pathlib
  import uuid
  from ipykernel.comm import Comm
  from IPython.display import display, Javascript, HTML
  from matplotlib import is_interactive
  from matplotlib._pylab_helpers import Gcf
  from matplotlib.backend_bases import _Backend, CloseEvent, NavigationToolbar2
  from .backend_webagg_core import FigureCanvasWebAggCore, FigureManagerWebAgg, NavigationToolbar2WebAgg
  from .backend_webagg_core import TimerTornado, TimerAsyncio
label_desc: Use image node_id 10 for calling the FigureManagerNbAgg obj's underlying member method code with example usage: obj.clearup_closed() without return types