[Fall 2021] Step 1: Pyre - Fix type checking errors in Pytorch `torch/quantization/fx/fusion_patterns.py`

[0xedward]

This task is part of a bigger effort to migrate Pytorch from Mypy to Pyre. The goal of this task for you is to gain comfort with the Python type system and the types of errors Pyre gives. Future Pysa project work and debugging builds on this foundation.

Development Environment Setup

• Set up Pytorch for development and run Mypy by following their contribution guide

Task Description

Fix the Pyre type checking errors in torch/quantization/fx/fusion_patterns.py:

torch/quantization/fx/fusion_patterns.py:25:13 Incompatible variable type [9]: fuse_custom_config_dict is declared to have type `Dict[str, typing.Any]` but is used as type `None`.
torch/quantization/fx/fusion_patterns.py:64:13 Incompatible variable type [9]: fuse_custom_config_dict is declared to have type `Dict[str, typing.Any]` but is used as type `None`.
torch/quantization/fx/fusion_patterns.py:121:13 Incompatible variable type [9]: fuse_custom_config_dict is declared to have type `Dict[str, typing.Any]` but is used as type `None`.

Submitting a PR

We use the following linters internally, so to save everyone's time, please make sure you run the following linters locally and fix errors related to the files you modified before submitting a PR:

black && usort format . && flake8

To install the linters, you can run the following command:

pip install flake8 usort black==21.4b2