/in/foo.cc:24:16: error: empty character constant
         return ''
                ^~
/in/foo.cc:2:9: error: expected class-name before '__init__'
     def __init__(self, mark):
         ^~~~~~~~
/in/foo.cc:2:9: error: expected '{' before '__init__'
/in/foo.cc:2:18: error: 'self' was not declared in this scope
     def __init__(self, mark):
                  ^~~~
/in/foo.cc:2:24: error: 'mark' was not declared in this scope
     def __init__(self, mark):
                        ^~~~
/in/foo.cc:2:28: error: expression list treated as compound expression in initializer [-fpermissive]
     def __init__(self, mark):
                            ^