Return the size of the directory given by path

        path: <string>

def __folder_size(self, path):
        """Return the size of the directory given by path

        path: <string>"""

        ret = 0
        for f in scandir(path):
            if f.is_dir() and (f.name != '.' or f.name != '..'):
                ret += self.__folder_size(os.path.join(path, f.name))
            else:
                try:
                    ret += f.stat().st_size
                except OSError:
                    pass

        return ret