Pipeline fails due to flake8 errors

[lupeterm]

Currently, the github actions fail because flake8 is throwing a multitude of undefined name errors.
A recent output:

./build/lib/Owls/io/io.py:240:15: F821 undefined name 'Origins'
    origins = Origins()
              ^
./build/lib/Owls/io/io.py:278:15: F821 undefined name 'Origins'
    origins = Origins()
              ^
./build/lib/Owls/parser/LogFile.py:123:34: F821 undefined name 'os'
        fold, dirs, files = next(os.walk(folder))
                                 ^
./build/lib/Owls/parser/LogFile.py:126:14: F821 undefined name 'DataFrame'
        df = DataFrame()
             ^
./build/lib/Owls/parser/LogFile.py:129:18: F821 undefined name 'concat'
            df = concat([df, self.parse_to_df(log_name)])
                 ^
./src/Owls/io/io.py:240:15: F821 undefined name 'Origins'
    origins = Origins()
              ^
./src/Owls/io/io.py:278:15: F821 undefined name 'Origins'
    origins = Origins()
              ^
./src/Owls/parser/LogFile.py:123:34: F821 undefined name 'os'
        fold, dirs, files = next(os.walk(folder))
                                 ^
./src/Owls/parser/LogFile.py:126:14: F821 undefined name 'DataFrame'
        df = DataFrame()
             ^
./src/Owls/parser/LogFile.py:129:18: F821 undefined name 'concat'
            df = concat([df, self.parse_to_df(log_name)])