Feat
- **pre-commit**: update black 21.5b0 -> 21.5b1
- **pre-commit**: update flake8 3.9.1 -> 3.9.2
- **pre-commit**: update black 21.4b2 -> 21.5b0
- **pre-commit**: update black 21.4b1 -> 21.4b2
- **pre-commit**: update black 21.4b0 -> 21.4b1
- **pre-commit**: update black 20.8b1 -> 21.4b0
- **pre-commit**: bump flake8 to 3.9.1
Refactor
- modify imports