code: def proxy_call_backward(
      self,
      inputs,
      output_metadatas,
      saved_tensors,
      backward_idx: int,
  ):
      assert self.hooks_proxy is not None
      backward_fn = self.hooks_proxy[backward_idx]
      proxies = self.fx_tracer.create_proxy(
          kind="call_function",
          target=call_backward,
          args=(
              backward_fn,
              self.to_proxy(saved_tensors),
              *self.to_proxy(inputs),
          ),
          kwargs={},
      )
  
      with disable_proxy_modes_tracing():
          # create fake Tensors
          grad_ins: List[Optional[torch.Tensor]] = []
          for output_metadata in output_metadatas:
              if output_metadata is None:
                  grad_ins.append(None)
                  continue
  
              layout, device, dtype, size = output_metadata
              grad_ins.append(
                  torch.empty(
                      size=size,
                      dtype=dtype,
                      layout=layout,
                      device=device,
                  )
              )
          self.bind_tensors_to_proxies(grad_ins, proxies)
      return tuple(grad_ins)
  
imports: import contextlib
  import functools
  from typing import List, Optional
  import torch
  from torch._dynamo.external_utils import call_backward, call_hook
  from torch._dynamo.source import GetItemSource, LocalSource
  from torch._dynamo.utils import counters, lazy_format_graph_code
  from torch._logging import getArtifactLogger
  from torch._prims_common import clone_preserve_strides
  from torch._subclasses import FakeTensorMode
  from torch.fx import GraphModule
  from torch.fx.experimental.proxy_tensor import decompose, disable_autocast_cache, disable_proxy_modes_tracing, fetch_tensor_proxy, ProxyTorchDispatchMode, PythonKeyTracer, track_tensor_tree
  from torch.fx.experimental.symbolic_shapes import DimDynamic, ShapeEnv
  from torch.fx.proxy import Proxy
label_desc: Use image node_id 5 for calling the AutogradCompilerInstance obj's underlying member method code with example usage: obj.proxy_call_backward(inputs, output_metadatas, saved_tensors, backward_idx) and returns: tuple