code: def tearDown(self) -> None:
      self.fl_server.stop()
  
imports: from multiprocessing import Process
  import unittest
  import numpy
  import os
  from bigdl.ppml.fl import *
  from bigdl.ppml.fl.estimator import Estimator
  from bigdl.ppml.fl.nn.fl_server import FLServer
  from bigdl.ppml.fl.nn.tensorflow.utils import set_one_like_parameter
  from bigdl.ppml.fl.nn.fl_context import init_fl_context
  from bigdl.ppml.fl.nn.tensorflow.estimator import TensorflowEstimator
  import tensorflow
  from tensorflow.keras.layers import Dense, Flatten, Conv2D, InputLayer
  from tensorflow.keras import Model, Input
label_desc: Use image node_id 2 for calling the TestCorrectness obj's underlying member method code with example usage: obj.tearDown() without return types