code: def get_arithmetic_coding_bpp(bitstring, bitstring_np, num_pixels):
      """Calculate bitrate we obtain with arithmetic coding."""
      # TODO(fab-jul): Add `compress` and `decompress` methods.
      packed = tfc.PackedTensors()
      packed.pack(tensors=bitstring, arrays=bitstring_np)
      return len(packed.string) * 8 / num_pixels
  
file_path: compression/models/hific/evaluate.py
imports: import argparse
  import collections
  import glob
  import itertools
  import os
  import sys
  import numpy
  from PIL import Image
  import tensorflow.compat.v1
  import tensorflow_compression
  from hific import configs
  from hific import helpers
  from hific import model
label_desc: Use image node_id 2 for calling a global function with example usage: get_arithmetic_coding_bpp(bitstring, bitstring_np, num_pixels) and returns: unknown