Useful:

• Running mypy and managing imports - mypy 1.12.0+dev.ecfab6a02415c46eda5717ec6ee9bfac8115c1e9.dirty documentation evergreen
• Error codes - mypy 1.12.0+dev.ecfab6a02415c46eda5717ec6ee9bfac8115c1e9.dirty documentation
• The mypy configuration file - mypy 1.12.0+dev.ecfab6a02415c46eda5717ec6ee9bfac8115c1e9.dirty documentation

mypy cares about packages, especially __init__.py files — the uppermost dir with such a file will be the root package. See Mapping files to modules - Running mypy and managing imports - mypy 1.12.0+dev.ecfab6a02415c46eda5717ec6ee9bfac8115c1e9.dirty documentation

This is needed to do per-package configs