docstr: generate the train_list.txt and val_list.txt
docstr_tok: ["generate","the","train_list.txt","and","val_list.txt"]
code: def generate_txt(self):
      """generate the train_list.txt and val_list.txt"""
      raise NotImplementedError
  
imports: import os
  import os.path
  import sys
  import time
  import glob
  import numpy
  import nibabel
  import SimpleITK
  from tqdm import tqdm
  import json
  from medicalseg.utils import get_image_list
  from tools.preprocess_utils import uncompressor, global_var, add_qform_sform, join_paths
label_desc: Use image node_id 6 for calling the Prep obj's underlying member method code with example usage: obj.generate_txt() without return types