class_docstr: The Tuning objective for HPO.
docstr: Set the target metric.
docstr_tok: ["Set","the","target","metric","."]
code: def target_metric(self, value):
      """Set the target metric."""
      # TODO add more validity check here
      self.target_metric_ = value
  
file_path: BigDL/python/nano/src/bigdl/nano/automl/tf/objective.py
imports: from selectors import EpollSelector
  from tensorflow.keras.backend import clear_session
  from tensorflow.keras.models import clone_model
  import tensorflow
  import inspect
  import copy
  from bigdl.nano.automl.hpo.backend import create_tfkeras_pruning_callback
  from bigdl.nano.utils.common import invalidInputError
label_desc: Use image node_id 3 for calling the Objective obj's underlying member method code with example usage: obj.target_metric(value) without return types