code: def _append_treatment_feature(
      features: list, treatment_feature: str
  ) -> list:
      return features + [treatment_feature]
  
imports: import copy
  import inspect
  from typing import Callable, Dict, List, Tuple
  import numpy
  import pandas
  from toolz import curry
  from fklearn.common_docstrings import learner_pred_fn_docstring, learner_return_docstring
  from fklearn.exceptions.exceptions import MissingControlError, MissingTreatmentError, MultipleTreatmentsError
  from fklearn.training.pipeline import build_pipeline
  from fklearn.types import LearnerFnType, LearnerReturnType, PredictFnType
label_desc: Use image node_id 1 for calling a global function with example usage: _append_treatment_feature(features, treatment_feature) and returns: unknown