class_docstr: This one finds a mask of nonzero elements (must be nonzero in all modalities) and crops the image to that mask.
  In the case of BRaTS and ISLES data this results in a significant reduction in image size.
  Args:
      num_threads (int): Number of threads. Default: None.
      output_folder (str, None): path to store the cropped data. Default: None.
code: def load_crop_save(
      self, case, case_identifier, overwrite_existing=False
  ):
      try:
          if overwrite_existing or (
              not os.path.isfile(
                  join_paths(
                      self.output_folder, "%s.npz" % case_identifier
                  )
              )
              or not os.path.isfile(
                  join_paths(
                      self.output_folder, "%s.pkl" % case_identifier
                  )
              )
          ):
              data, seg, properties = self.crop_from_list_of_files(
                  case[:-1], case[-1]
              )
  
              all_data = np.vstack((data, seg))
              np.savez_compressed(
                  join_paths(
                      self.output_folder, "%s.npz" % case_identifier
                  ),
                  data=all_data,
              )
              with open(
                  join_paths(
                      self.output_folder, "%s.pkl" % case_identifier
                  ),
                  "wb",
              ) as f:
                  pickle.dump(properties, f)
      except Exception as e:
          raise UserWarning(
              "Exception occurs when crop {}, exception info: {}.".format(
                  case_identifier, e
              )
          )
  
imports: import os
  import json
  import shutil
  import pickle
  import numpy
  import SimpleITK
  from scipy.ndimage import binary_fill_holes
  from multiprocessing import Pool
  from collections import OrderedDict
  from .path_utils import join_paths
label_desc: Use image node_id 4 for calling the ImageCropper obj's underlying member method code with example usage: obj.load_crop_save(case, case_identifier, overwrite_existing) without return types