Exposes bug with DataParallel when using dicts as input

bug.py

import torch
import torch.nn as nn
from torch.autograd import Variable

class SimpleModel(nn.Module):
	def __init__(self):
		super(SimpleModel, self).__init__()
		self.net = nn.Linear(10, 2)

	def forward(self, inputs):
		return self.net(inputs['data'])

net = nn.DataParallel(SimpleModel()).cuda()

inputs = {'data': Variable(torch.rand(10, 10).cuda())}
outputs = net(inputs)
print(outputs)

"""
# Works fine on single device as DataParallel defaults to simple execution if one device only.
$ CUDA_VISIBLE_DEVICES=0 python bug.py 
Variable containing:
-0.1836  0.2654
-0.3584  0.0049
-0.2587 -0.0808
-0.2482 -0.2587
-0.4238 -0.2014
-0.1964 -0.1709
-0.6334 -0.0843
-0.4466  0.1243
-0.5991 -0.2169
-0.3005 -0.0565
[torch.cuda.FloatTensor of size 10x2 (GPU 0)]

# Fails on multiple devices.
$ CUDA_VISIBLE_DEVICES=0,1 python bug.py 
Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib/python3.5/threading.py", line 914, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.5/threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
  File "venv/lib/python3.5/site-packages/torch/nn/parallel/parallel_apply.py", line 22, in _worker
    var_input = var_input[0]
KeyError: 0

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python3.5/threading.py", line 914, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.5/threading.py", line 862, in run
    self._target(*self._args, **self._kwargs)
  File "venv/lib/python3.5/site-packages/torch/nn/parallel/parallel_apply.py", line 22, in _worker
    var_input = var_input[0]
KeyError: 0

Traceback (most recent call last):
  File "bug.py", line 16, in <module>
    outputs = net(inputs)
  File "venv/lib/python3.5/site-packages/torch/nn/modules/module.py", line 206, in __call__
    result = self.forward(*input, **kwargs)
  File "venv/lib/python3.5/site-packages/torch/nn/parallel/data_parallel.py", line 61, in forward
    outputs = self.parallel_apply(replicas, inputs, kwargs)
  File "venv/lib/python3.5/site-packages/torch/nn/parallel/data_parallel.py", line 71, in parallel_apply
    return parallel_apply(replicas, inputs, kwargs)
  File "venv/lib/python3.5/site-packages/torch/nn/parallel/parallel_apply.py", line 44, in parallel_apply
    output = results[i]
KeyError: 0
"""