remove all compatibility code (v4.0.0)

Author: syntron

.github/workflows/Test_v400.yml

@@ -33,7 +33,7 @@ repos:
     hooks:
       - id: mypy
         args: []
-        exclude: 'test|test_v400'
+        exclude: 'test'
         additional_dependencies:
           - pyparsing
           - types-psutil