code: def test_server(self):
      arena = dx.Arena()
      arena.push_model(self.exp)
      arena.push_model(self.exp2)
      port = get_free_port()
      try:
          arena.run_server(port=port)
          time.sleep(2)
          self.assertFalse(try_port(port))
          arena.stop_server()
      except AssertionError as e:
          arena.stop_server()
          raise e
  
imports: import unittest
  from plotly.graph_objs import Figure
  from sklearn.compose import ColumnTransformer
  from sklearn.impute import SimpleImputer
  from sklearn.neural_network import MLPClassifier
  from sklearn.pipeline import Pipeline
  from sklearn.preprocessing import StandardScaler, LabelEncoder, OneHotEncoder
  import dalex
  import time
  import numpy
  import pandas
  from dalex.arena.static import get_free_port, try_port
  from dalex.arena.plots import *
label_desc: Use image node_id 3 for calling the ArenaTestTitanic obj's underlying member method code with example usage: obj.test_server() without return types