*torch.device) -- local devices used by the TensorPipe RPC
         agent.
Note:
The RPC framework does not automatically retry any "rpc_sync()",
  "rpc_async()" and "remote()" calls. The reason being that there is
  no way the RPC framework can determine whether an operation is
  idempotent or not and whether it is safe to retry. As a result, it
  is the application's responsibility to deal with failures and retry
  if necessary. RPC communication is based on TCP and as a result
  failures could happen due to network failures or intermittent
  network connectivity issues. In such scenarios, the application
  needs to retry appropriately with reasonable backoffs to ensure the
  network isn't overwhelmed by aggressive retries.
RRef
Warning:
RRefs are not currently supported when using CUDA tensors
An "RRef" (Remote REFerence) is a reference to a value of some type
"T" (e.g. "Tensor") on a remote worker. This handle keeps the
referenced remote value alive on the owner, but there is no