code: def cv_fold_index(n, i, k, random_seed=2018):
      """
      Encoding string features.
  
      Args
      ----
  
      dfx : dataframe
          The inputs data dataframe.
  
      kpix : string
          The column of the feature.
  
      kpi1 : list
          The list of feature names.
  
      Returns
      -------
      dfx : DataFrame
          The updated dataframe containing the encoded data.
  
      kpi1 : list
          The updated feature names containing the new dummy feature names.
      """
      np.random.seed(random_seed)
      rlist = np.random.choice(a=range(k), size=n, replace=True)
      fold_i_index = np.where(rlist == i)[0]
      return fold_i_index
  
file_path: causalml/causalml/inference/tree/utils.py
imports: import time
  from typing import Callable
  import numpy
  import pandas
label_desc: Use image node_id 3 for calling a global function with example usage: cv_fold_index(n, i, k, random_seed) and returns: fold_i_index