code: def remove_postfix(folder=".", post_fix=".pkl"):
      import os
  
      for f in os.listdir(folder):
          if os.path.isfile(f) and f.endswith(post_fix):
              os.remove(os.path.join(folder, f))
  
imports: import os
  import pytest
  import subprocess
  from io import StringIO
  import sys
  from fastNLP.core.utils.cache_results import cache_results
  from fastNLP.envs.distributed import rank_zero_rm
label_desc: Use image node_id 2 for calling a global function with example usage: remove_postfix(folder, post_fix) without return types