Add and apply some mypy rules

mypy.ini

@@ -7,3 +7,9 @@ no_implicit_optional = True
 warn_return_any = True
 show_error_codes = True
 warn_unused_ignores = True
+
+disallow_incomplete_defs = true
+disallow_subclassing_any = true
+disallow_untyped_calls = true
+disallow_untyped_decorators = true
+warn_unreachable = true