code: def test_teardown(xla_available):
      plugin = XLAPrecision(precision="16-true")
      assert os.environ["XLA_USE_F16"] == "1"
      plugin.teardown()
      assert "XLA_USE_B16" not in os.environ
  
      plugin = XLAPrecision(precision="bf16-true")
      assert os.environ["XLA_USE_BF16"] == "1"
      plugin.teardown()
      assert "XLA_USE_BF16" not in os.environ
  
file_path: pytorch-lightning/tests/tests_fabric/plugins/precision/test_xla.py
imports: import os
  import re
  from unittest import mock
  import pytest
  import torch
  from lightning.fabric.plugins import XLAPrecision
label_desc: Use image node_id 3 for calling a global function with example usage: test_teardown(xla_available) without return types