code: def _init_backend(platform: str) -> xla_client.Client:
      registration = _backend_factories.get(platform, None)
      if registration is None:
          raise RuntimeError(
              f"Backend '{platform}' is not in the list of known backends: "
              f"{list(_backend_factories.keys())}."
          )
  
      if registration.experimental:
          logger.warning(
              f"Platform '{platform}' is experimental and not all JAX "
              "functionality may be correctly supported!"
          )
      logger.debug("Initializing backend '%s'", platform)
      backend = registration.factory()
      # TODO(skye): consider raising more descriptive errors directly from backend
      # factories instead of returning None.
      if backend is None:
          raise RuntimeError(
              f"Could not initialize backend '{platform}'"
          )
      if backend.device_count() == 0:
          raise RuntimeError(
              f"Backend '{platform}' provides no devices."
          )
      util.distributed_debug_log(
          ("Initialized backend", backend.platform),
          ("process_index", backend.process_index()),
          ("device_count", backend.device_count()),
          ("local_devices", backend.local_devices()),
      )
      logger.debug("Backend '%s' initialized", platform)
      return backend
  
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 21 for calling a global function with example usage: _init_backend(platform) and returns: backend