def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def log_stream(self, logger_name, level_name, format_str):
        """ Attaches a log handler to the specified logger and sends emitted logs 
            back as stream. 
        """
        if logger_name != "" and logger_name not in self.available_loggers():
            raise ValueError("logger {0} is not available".format(logger_name))

        level_name_upper = level_name.upper() if level_name else "NOTSET"
        try:
            level = getattr(logging, level_name_upper)
        except AttributeError, e:
            raise AttributeError("log level {0} is not available".format(level_name_upper))