def format_treevisitor_str(treevisitor_str: str):
    """
    Transform a string like "(message & author)" into ["message", "author"]
    or "(message)" into ["message"]
    """
    if not treevisitor_str.startswith("("):
        return [treevisitor_str]
    treevisitor_str = treevisitor_str.removeprefix("(").removesuffix(")")
    if "&" in treevisitor_str:
        word_list = treevisitor_str.split("&")
        for i, _ in enumerate(word_list):
            word_list[i] = word_list[i].strip('" ')
        return word_list
    return [treevisitor_str.strip().removeprefix('"').removesuffix('"')]