code: def ensure_initialized():
      with FLClient._lock:
          if FLClient.channel == None:
              if FLClient.secure:
                  FLClient.channel = grpc.secure_channel(
                      FLClient.target, FLClient.creds
                  )
              else:
                  FLClient.channel = grpc.insecure_channel(
                      FLClient.target
                  )
  
file_path: BigDL/python/ppml/src/bigdl/ppml/fl/nn/fl_client.py
imports: import logging
  import grpc
  from bigdl.ppml.fl.nn.generated.nn_service_pb2 import TrainRequest, PredictRequest, UploadMetaRequest
  from bigdl.ppml.fl.nn.generated.nn_service_pb2_grpc import *
  import yaml
  import threading
  from bigdl.dllib.utils.log4Error import invalidInputError
label_desc: Use image node_id 3 for calling the FLClient obj's underlying member method code with example usage: obj.ensure_initialized() without return types