### Guidelines

**NOTE:** Issues are for bugs and feature requests only. If you have a question about using Pyro or general modeling questions, please post it on the [forum](https://forum.pyro.ai/).

If you would like to address any minor bugs in the documentation or source, please feel free to contribute a Pull Request without creating an issue first. 

Please tag the issue appropriately in the title e.g. [bug], [feature request], [discussion], etc.

Please provide the following details:
--------------------------------------------------------------------------------------------------
### Issue Description
Provide a brief description of the issue.

### Environment
For any bugs, please provide the following:
 - OS and python version.
 - PyTorch version, or if relevant, output of `pip freeze`.
 - Pyro version: output of `python -c 'import pyro; print pyro.__version__'`

### Code Snippet
Provide any relevant code snippets and commands run to replicate the issue.
