class_docstr: Extract image feature using pretrained CNN network.
class_docstr_tok: ["Extract","image","feature","using","pretrained","CNN","network","."]
code: def _image_mode_switcher(self):
      if self.image_mode not in IMAGE_MODE_SWITCHER:
          raise NotImplementedError(
              "image preprocessing mode"
              + "{} not supported yet".format(self.image_mode)
          )
  
      return IMAGE_MODE_SWITCHER.get(self.image_mode)
  
imports: import parlai.core.build_data
  import parlai.utils.logging
  from parlai.utils.io import PathManager
  import os
  from PIL import Image
  import torch
  from zipfile import ZipFile
label_desc: Use image node_id 6 for calling the ImageLoader obj's underlying member method code with example usage: obj._image_mode_switcher() and returns: IMAGE_MODE_SWITCHER