code: def get_class_proportions():
      """Returns a [num_classes] array of pixel frequency proportions."""
      p = [
          PIXELS_PER_CID[c.id] for c in CLASSES if not c.ignore_in_eval
      ]
      return np.array(p) / np.sum(p)
  
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 6 for calling a global function with example usage: get_class_proportions() and returns: unknown