code: def file_usage(path):
      """Calculate the size used by the files in bytes."""
      size = 0
      for root, _, files in os.walk(path):
          for filename in files:
              size += os.stat(os.path.join(root, filename)).st_size
      return size
  
file_path: pystan/tests/test_fit_cache.py
imports: import os
  import pathlib
  import random
  import httpstan.cache
  import stan
label_desc: Use image node_id 2 for calling a global function with example usage: file_usage(path) and returns: size