def METHOD_NAME(self, partial_path):
    if partial_path is None:
        self._folders_in_current_dir = set([Path(a).parts[0] for a in self.entries.keys()])
    else:
        partial_path = Path(partial_path).as_posix().lower()
        self._folders_in_current_dir.clear()
        for filepath in self.entries.keys():
            tmp = Path(filepath).parent.as_posix().lower()
            if tmp.startswith(partial_path):
                self._folders_in_current_dir.add(Path(filepath).relative_to(partial_path).parts[0])
    yield from self._folders_in_current_dir