code: def mp_pack(inputs):
      ix, f = inputs
      file_path, source_dir, target_dir = f
      print("packing file number: {}".format(ix))
      if "npy" in file_path:
          source_path = os.path.join(source_dir, file_path)
          target_path = os.path.join(
              target_dir, file_path.split(".")[0] + ".npz"
          )
          arr = np.load(source_path, mmap_mode="r")
          np.savez_compressed(target_path, data=arr)
          print("target_path", target_path)
  
file_path: medicaldetectiontoolkit/experiments/lidc_exp/pack_dataset.py
imports: import numpy
  from multiprocessing import Pool
  import os
  import subprocess
label_desc: Use image node_id 5 for calling a global function with example usage: mp_pack(inputs) without return types