code: def _get_chunk_key(filenames):
      # lists are not hashable so key on the first filename in a chunk
      return filenames[0]
  
file_path: arrow/cpp/build-support/run_cpplint.py
imports: from __future__ import print_function
  import lintutils
  from subprocess import PIPE, STDOUT
  import argparse
  import multiprocessing
  import sys
  import platform
  from functools import partial
label_desc: Use image node_id 1 for calling a global function with example usage: _get_chunk_key(filenames) and returns: filenames