def remove_inner_brackets(message: str) -> str:
    """Remove the inner brackets i.e., [ or ], from a string, outer brackets are kept.

    Parameters
    ----------
    message: str
        The string to remove the inner brackets from.

    Returns
    -------
    str:
        A new message without any inner brackets.

    """
    level = 0
    new_message = ""
    for char in message:
        if char == "[":
            if level == 0:
                new_message += char
            level += 1
        elif char == "]":
            if level == 1:
                new_message += char
            level -= 1
        else:
            new_message += char
        assert level >= 0
    return new_message