code: def test_callback_update_graph(self):
      with subprocess.Popen(
          ["python", "-m", "visdom.server", "-port", str(self.port)]
      ) as proc:
          # wait for visdom server startup (any better way?)
          viz = Visdom(server=self.host, port=self.port)
          for attempt in range(5):
              time.sleep(1.0)  # seconds
              if viz.check_connection():
                  break
          assert viz.check_connection()
          viz.close()
          self.model.update(self.corpus)
          proc.kill()
  
file_path: gensim/gensim/test/test_lda_callback.py
imports: import unittest
  import subprocess
  import time
  from gensim.models import LdaModel
  from gensim.test.utils import datapath, common_dictionary
  from gensim.corpora import MmCorpus
  from gensim.models.callbacks import CoherenceMetric
label_desc: Use image node_id 2 for calling the TestLdaCallback obj's underlying member method code with example usage: obj.test_callback_update_graph() without return types