code: def default_hp_search_backend() -> str:
      available_backends = [
          backend
          for backend in ALL_HYPERPARAMETER_SEARCH_BACKENDS.values()
          if backend.is_available()
      ]
      if len(available_backends) > 0:
          name = available_backends[0].name
          if len(available_backends) > 1:
              logger.info(
                  f"{len(available_backends)} hyperparameter search backends available. Using {name} as the default."
              )
          return name
      raise RuntimeError(
          "No hyperparameter search backend available.\n"
          + "\n".join(
              f" - To install {backend.name} run {backend.pip_install()}"
              for backend in ALL_HYPERPARAMETER_SEARCH_BACKENDS.values()
          )
      )
  
imports: from .integrations import is_optuna_available, is_ray_tune_available, is_sigopt_available, is_wandb_available, run_hp_search_optuna, run_hp_search_ray, run_hp_search_sigopt, run_hp_search_wandb
  from .trainer_utils import HPSearchBackend, default_hp_space_optuna, default_hp_space_ray, default_hp_space_sigopt, default_hp_space_wandb
  from .utils import logging
label_desc: Use image node_id 1 for calling a global function with example usage: default_hp_search_backend() and returns: name