code: def get_post_exclusion_labels():
      """Determines new labels after excluding bad classes.
  
      See Figure 1 in https://arxiv.org/abs/1604.01685 for which classes are
      excluded. Excluded classes get the new label -1.
  
      Returns:
        An array of length num_old_classes, containing new labels.
      """
      old_to_new_labels = np.array(
          [-1 if c.ignore_in_eval else c.train_id for c in CLASSES]
      )
      assert np.all(
          np.diff([i for i in old_to_new_labels if i >= 0]) == 1
      )
      return old_to_new_labels
  
file_path: scenic/scenic/dataset_lib/cityscapes_dataset.py
imports: import collections
  import functools
  from typing import Optional
  from absl import logging
  import jax.numpy
  import numpy
  from scenic.dataset_lib import dataset_utils
  from scenic.dataset_lib import datasets
  import tensorflow
label_desc: Use image node_id 3 for calling a global function with example usage: get_post_exclusion_labels() and returns: old_to_new_labels