def check_index(index: str, values: list, messages: list) -> bool:
    """Checks that min-max values are a two-items list.

    Parameters
    ----------
    index : str
        Numeric indicator.
    values : list
        Metadata variables in criteria.
    messages : list
        Message to print in case of error.

    Returns
    -------
    boolean : bool
        Whether to keep the key/value or not.

    """
    boolean = False
    if index == '2' and len(values) != 2:
        messages.append('For min-max subsetting, two-items list need: no min (or no max) should be "None"')
        boolean = True
    return boolean