code: def backends() -> dict[str, xla_client.Client]:
      global _backends
      global _backend_errors
      global _default_backend
      global _plugins_registered
  
      # Needs a separate lock because register_backend_factory (called from
      # register_plugin) requries to hold _backend_lock.
      with _plugin_lock:
          if not _plugins_registered:
              # Plugins in the namespace package `jax_plugins` or have an entry-point
              # under the `jax_plugins` group will be imported.
              discover_pjrt_plugins()
              # Registers plugins names and paths set in env var
              # PJRT_NAMES_AND_LIBRARY_PATHS, in the format of 'name1:path1,name2:path2'
              # ('name1;path1,name2;path2' for windows).
              register_pjrt_plugin_factories_from_env()
              _plugins_registered = True
  
      with _backend_lock:
          if _backends:
              return _backends
          if jax_platforms := config.jax_platforms.value:
              platforms = []
              # Allow platform aliases in the list of platforms.
              for platform in jax_platforms.split(","):
                  platforms.extend(expand_platform_alias(platform))
              priorities = range(len(platforms), 0, -1)
              # If the user specified a list of platforms explicitly, always fail
              # loudly.
              fail_quietly_list = [False] * len(platforms)
              platform_registrations = list(
                  zip(platforms, priorities, fail_quietly_list)
              )
          else:
              platform_registrations = [
                  (
                      platform,
                      registration.priority,
                      registration.fail_quietly,
                  )
                  for platform, registration in _backend_factories.items()
              ]
          default_priority = -1000
          for (
              platform,
              priority,
              fail_quietly,
          ) in platform_registrations:
              try:
                  backend = _init_backend(platform)
                  _backends[platform] = backend
  
                  if priority > default_priority:
                      _default_backend = backend
                      default_priority = priority
              except Exception as err:
                  err_msg = f"Unable to initialize backend '{platform}': {err}"
                  if fail_quietly:
                      _backend_errors[platform] = str(err)
                      logger.info(err_msg)
                  else:
                      if config.jax_platforms.value:
                          err_msg += " (set JAX_PLATFORMS='' to automatically choose an available backend)"
                      else:
                          err_msg += " (you may need to uninstall the failing plugin package, or set JAX_PLATFORMS=cpu to skip this backend.)"
                      raise RuntimeError(err_msg)
  
          assert _default_backend is not None
          if not config.jax_platforms.value:
              _suggest_missing_backends()
          return _backends
  
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 18 for calling a global function with example usage: backends() and returns: _backends, _backends