code: def handle_ack(self, event):
      # Network latency tends to decrease if traffic is flowing
      # in both directions.  Therefore, the browser sends back
      # an "ack" message after each image frame is received.
      # This could also be used as a simple sanity check in the
      # future, but for now the performance increase is enough
      # to justify it, even if the server does nothing with it.
      pass
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import datetime
  import io
  import json
  import os
  import warnings
  import numpy
  import tornado
  from matplotlib.backends import backend_agg
  from matplotlib.backend_bases import _Backend
  from matplotlib import backend_bases
  from matplotlib import _png
label_desc: Use image node_id 10 for calling the FigureCanvasWebAggCore obj's underlying member method code with example usage: obj.handle_ack(event) without return types