def METHOD_NAME(command_name=None) -> List[str]:
    """
    Returns the helper docstring for the given command. If no command is
    specified, returns a sorted list of all the bot's command helper docstrings.
    Otherwise, will return a list of length 1. Will filter out any commands that
    do not have a valid helper docstring (see 'is_valid_helper_doc' function).
    """
    # functions matching this command, possibly with duplicates
    fns = (fn for command, functions in uqcsbot.bot._command_registry.items()
           for fn in functions
           if command_name is None or command_name == command)
    # we need to remove duplicates after getting docs because @bot.on_command
    # makes distinct copies of functions for aliases.
    docs = set(sanitize_doc(fn.__doc__) for fn in fns
               if is_valid_helper_doc(fn.__doc__))
    return list(sorted(docs))