update mypy to 0.670
update mypy to 0.670

sbidoul/pip,rouge8/pip,xavfernandez/pip,sbidoul/pip,pradyunsg/pip,pypa/pip,rouge8/pip,xavfernandez/pip,pfmoore/pip,pypa/pip,pfmoore/pip,xavfernandez/pip,rouge8/pip,pradyunsg/pip