code: def make_ca():
      os.mkdir(TMP_CADIR)
      with open(os.path.join("cadir", "index.txt"), "a+") as f:
          pass  # empty file
      # with open(os.path.join('cadir','crl.txt'),'a+') as f:
      # f.write("00")
      with open(os.path.join("cadir", "index.txt.attr"), "w+") as f:
          f.write("unique_subject = no")
  
      with tempfile.NamedTemporaryFile("w") as t:
          t.write(req_template.format(hostname="our-ca-server"))
          t.flush()
          with tempfile.NamedTemporaryFile() as f:
              args = [
                  "req",
                  "-new",
                  "-days",
                  "365242",
                  "-extensions",
                  "v3_ca",
                  "-nodes",
                  "-newkey",
                  "rsa:2048",
                  "-keyout",
                  "tls-ca-key.pem",
                  "-out",
                  f.name,
                  "-subj",
                  "/C=XY/L=Dask-distributed/O=Dask CA/CN=our-ca-server",
              ]
              subprocess.check_call(["openssl"] + args)
              args = [
                  "ca",
                  "-config",
                  t.name,
                  "-create_serial",
                  "-out",
                  "tls-ca-cert.pem",
                  "-batch",
                  "-outdir",
                  TMP_CADIR,
                  "-keyfile",
                  "tls-ca-key.pem",
                  "-days",
                  "365242",
                  "-selfsign",
                  "-extensions",
                  "v3_ca",
                  "-infiles",
                  f.name,
              ]
              subprocess.check_call(["openssl"] + args)
  
file_path: distributed/distributed/tests/make_tls_certs.py
imports: from __future__ import annotations
  import os
  import shutil
  import subprocess
  import tempfile
label_desc: Use image node_id 3 for calling a global function with example usage: make_ca() without return types