code: def _suggest_missing_backends():
      if py_platform.system() != "Linux":
          # If you're not using Linux (or WSL2), we don't have any suggestions at the
          # moment.
          return
  
      assert _default_backend is not None
      default_platform = _default_backend.platform
      nvidia_gpu_devices = [
          "/dev/nvidia0",
          "/dev/dxg",  # WSL2
      ]
      if "cuda" not in _backends and any(
          os.path.exists(d) for d in nvidia_gpu_devices
      ):
          if (
              hasattr(xla_extension, "GpuAllocatorConfig")
              and "cuda" in _backend_errors
          ):
              err = _backend_errors["cuda"]
              logger.warning(
                  f"CUDA backend failed to initialize: {err} (Set "
                  "TF_CPP_MIN_LOG_LEVEL=0 and rerun for more info.)"
              )
          else:
              logger.warning(
                  "An NVIDIA GPU may be present on this machine, but a "
                  "CUDA-enabled jaxlib is not installed. Falling back to "
                  f"{default_platform}."
              )
      elif (
          "tpu" not in _backends
          and hardware_utils.num_available_tpu_chips_and_device_id()[0]
          > 0
      ):
          logger.warning(
              "A Google TPU may be present on this machine, but either a "
              "TPU-enabled jaxlib or libtpu is not installed. Falling "
              f"back to {default_platform}."
          )
  
imports: from __future__ import annotations
  from __future__ import annotations
  from collections.abc import Mapping
  import dataclasses
  from functools import lru_cache, partial
  import importlib
  import json
  import logging
  import os
  import pkgutil
  import platform
  import sys
  import threading
  from typing import Any, Callable, Union
  import warnings
  from jax._src import config
  from jax._src import distributed
  from jax._src import traceback_util
  from jax._src import util
  from jax._src import hardware_utils
  from jax._src.cloud_tpu_init import maybe_import_libtpu
  from jax._src.lib import cuda_versions
  from jax._src.lib import xla_client
  from jax._src.lib import xla_extension
  from jax._src.lib import xla_extension_version
label_desc: Use image node_id 19 for calling a global function with example usage: _suggest_missing_backends() without return types