code: def _strip_val_prefix(metric):
      if metric.startswith("val_"):
          metric = metric[len("val_") :]
      return metric
  
file_path: BigDL/python/nano/src/bigdl/nano/automl/hpo/search.py
imports: import optuna
  from bigdl.nano.utils.common import invalidInputError
label_desc: Use image node_id 8 for calling a global function with example usage: _strip_val_prefix(metric) and returns: metric