code: def available_backends() -> Tuple[str, ...]:
      """Returns available backends."""
      out: Tuple[str, ...] = ()
      for m in registered_computation_models:
          out += m.available_backends
      return out
  
imports: import socket
  from contextlib import contextmanager
  from functools import wraps
  from typing import Any, Callable, List, Mapping, Optional, Tuple, Union
  import torch
  from ignite.distributed.comp_models import _SerialModel, has_hvd_support, has_native_dist_support, has_xla_support, registered_computation_models
  from ignite.utils import setup_logger
label_desc: Use image node_id 4 for calling a global function with example usage: available_backends() and returns: out