class_docstr: Helper class which loads and stores dataset metadata.
docstr: Saves target classed for all dataset images into given file.
docstr_tok: ["Saves","target","classed","for","all","dataset","images","into","given","file","."]
code: def save_target_classes(self, filename):
      """Saves target classed for all dataset images into given file."""
      with open(filename, "w") as f:
          for k, v in self._target_classes.items():
              f.write("{0}.png,{1}\n".format(k, v))
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import argparse
  import csv
  import json
  import os
  import subprocess
  import numpy
  from PIL import Image
label_desc: Use image node_id 4 for calling the DatasetMetadata obj's underlying member method code with example usage: obj.save_target_classes(filename) without return types