Added a few extra python bindings to help with walking the IR graph from Python (#17822)
Summary:
These changes add the following new Python bindings:
- Values have a 'type' property now that allows getting to the 'type' object
- Blocks have now inputs and outputs as well as returnNode and paramNode properties
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17822
Differential Revision: D14410123
Pulled By: ezyang
fbshipit-source-id: 64ef79f85a7a43b83e4b127b1d39efcaa64b74dc
