Error with Hierarchical intent and slot filling sample

[deepali-c]

Steps to reproduce

1. Execute the Hierarchical intent and slot filling sample with smaller dataset with PyTorch v1.4.0 and Pytext v0.3.1

Observed Results

Observed the following error:

=== Saving model to: <mydir>/pytext/model.pt
Saving pytorch model to: <mydir>/pytext/model.pt
Exporting metrics
Tracer cannot infer type of (tensor([[ 2,  3,  4,  5,  6,  7,  8,  9, 10,  7, 11]]), tensor([11]), None, [[0, 1, 1, 1, 1, 1, 1, 2, 1, 3, 1, 4, 1, 3, 1, 5, 1, 3, 3]], None)
:Cannot infer type of a None value (toTraceableIValue at <mypytorchwork>/torch/csrc/jit/pybind_utils.h:286)
frame #0: c10::Error::Error(c10::SourceLocation, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) + 0xbc (0x7fff38247b9c in 
...
...
Error occurs, No graph saved
WARNING: Unable to export neural network graph to TensorBoard.
Traceback (most recent call last):
  File "<myenv>/lib/python3.6/site-packages/pytext/metric_reporters/channel.py", line 312, in export
    self.summary_writer.add_graph(model, input_to_model, **kwargs)
  File "<myenv>/lib/python3.6/site-packages/torch/utils/tensorboard/writer.py", line 682, in add_graph
    self._get_file_writer().add_graph(graph(model, input_to_model, verbose))
  File "<myenv>/lib/python3.6/site-packages/torch/utils/tensorboard/_pytorch_graph.py", line 239, in graph
    raise e
  File "<myenv>/lib/python3.6/site-packages/torch/utils/tensorboard/_pytorch_graph.py", line 234, in graph
    trace = torch.jit.trace(model, args)
  File "<myenv>/lib/python3.6/site-packages/torch/jit/__init__.py", line 858, in trace
    check_tolerance, _force_outplace, _module_class)
  File "<myenv>/lib/python3.6/site-packages/torch/jit/__init__.py", line 997, in trace_module
    module._c._create_method_from_trace(method_name, func, example_inputs, var_lookup_fn, _force_outplace)
RuntimeError: Tracer cannot infer type of (tensor([[ 2,  3,  4,  5,  6,  7,  8,  9, 10,  7, 11]]), tensor([11]), None, [[0, 1, 1, 1, 1, 1, 1, 2, 1, 3, 1, 4, 1, 3, 1, 5, 1, 3, 3]], None)
:Cannot infer type of a None value (toTraceableIValue at <mypytorchwork/torch/csrc/jit/pybind_utils.h:286)
frame #0: c10::Error::Error(c10::SourceLocation, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) + 0xbc (0x7fff38247b9c in 

Expected Results

The sample should sucessfully run.