code: def load_from_ceph(filename, map_location=None, backend="petrel"):
      """load checkpoint through the file path prefixed with s3.  In distributed
      setting, this function download ckpt at all ranks to different temporary
      directories.
  
      Args:
          filename (str): checkpoint file path with s3 prefix
          map_location (str, optional): Same as :func:`torch.load`.
          backend (str, optional): The storage backend type. Options are 'ceph',
              'petrel'. Default: 'petrel'.
  
      .. warning::
          :class:`mmcv.fileio.file_client.CephBackend` will be deprecated,
          please use :class:`mmcv.fileio.file_client.PetrelBackend` instead.
  
      Returns:
          dict or OrderedDict: The loaded checkpoint.
      """
      allowed_backends = ["ceph", "petrel"]
      if backend not in allowed_backends:
          raise ValueError(
              f"Load from Backend {backend} is not supported."
          )
  
      if backend == "ceph":
          warnings.warn(
              "CephBackend will be deprecated, please use PetrelBackend instead"
          )
  
      # CephClient and PetrelBackend have the same prefix 's3://' and the latter
      # will be chosen as default. If PetrelBackend can not be instantiated
      # successfully, the CephClient will be chosen.
      try:
          file_client = FileClient(backend=backend)
      except ImportError:
          allowed_backends.remove(backend)
          file_client = FileClient(backend=allowed_backends[0])
  
      with io.BytesIO(file_client.get(filename)) as buffer:
          checkpoint = torch.load(buffer, map_location=map_location)
      return checkpoint
  
imports: import io
  import os
  import os.path
  import pkgutil
  import re
  import time
  import warnings
  from collections import OrderedDict
  from importlib import import_module
  from tempfile import TemporaryDirectory
  import torch
  import torchvision
  from torch.optim import Optimizer
  from torch.utils import model_zoo
  import annotator.uniformer.mmcv
  from ..fileio import FileClient
  from ..fileio import load
  from ..parallel import is_module_wrapper
  from ..utils import mkdir_or_exist
  from .dist_utils import get_dist_info
label_desc: Use image node_id 11 for calling a global function with example usage: load_from_ceph(filename, map_location, backend) and returns: checkpoint