code: def test_env_var():
      check_env_var("system", ["system"])
      if should_have_jemalloc:
          check_env_var("jemalloc", ["jemalloc"])
      if should_have_mimalloc:
          check_env_var("mimalloc", ["mimalloc"])
      check_env_var(
          "nonexistent", possible_backends, expect_warning=True
      )
  
imports: import contextlib
  import os
  import signal
  import subprocess
  import sys
  import weakref
  import pyarrow
  import pytest
label_desc: Use image node_id 11 for calling a global function with example usage: test_env_var() without return types