docstr: generate the train_list.txt and val_list.txt
code: def generate_txt(self, split=0.2):
      """generate the train_list.txt and val_list.txt"""
  
      txtname = [
          join_paths(self.phase_path, "train_list.txt"),
          join_paths(self.phase_path, "val_list.txt"),
      ]
      val_len = int(split * len(self.filenames))
  
      with open(txtname[0], "w") as f:
          for filename in self.filenames[:-val_len]:
              f.write(
                  "images/{}.npy labels/{}.npy\n".format(
                      filename, filename
                  )
              )
      with open(txtname[1], "w") as f:
          for filename in self.filenames[-val_len:]:
              f.write(
                  "images/{}.npy labels/{}.npy\n".format(
                      filename, filename
                  )
              )
  
file_path: PaddleSeg/contrib/MedicalSeg/tools/prepare_acdc.py
imports: import nibabel
  import shutil
  import os.path
  from preprocess_utils.file_and_folder_operations import *
  from preprocess_utils.geometry import *
  from preprocess_utils.path_utils import join_paths
  from tqdm import tqdm
label_desc: Use image node_id 2 for calling the PrepACDC obj's underlying member method code with example usage: obj.generate_txt(split) without return types