Fix 6 Maintainability issues in multiple files

[matfax]

CodeFactor found multiple issues:

Unnecessary "else" after "return"

mutapath\decorator.py:84
Commit a2e0cd1

Unnecessary "elif" after "return"

mutapath\decorator.py:86
Commit 4a9cf29

Unnecessary pass statement

mutapath\lock_dummy.py:20
Commit a2e0cd1
mutapath\lock_dummy.py:16
Commit a2e0cd1
mutapath\lock_dummy.py:12
Commit a2e0cd1
mutapath\lock_dummy.py:8
Commit a2e0cd1