def countBlank(series, blanks = [None]):
    """Count number and percentage of blank values in series

    Args:
        series (Series): data series
        blanks (list): list of blank values

    Returns:
        number: number of blanks
        str: the percentage of blank values
    """
    # n = 0
    # counts = series.value_counts()
    # for blank in blanks:
    #     if blank in counts.keys():
    #         n += counts[blank]

    n = series.isnull().sum()

    return (n, "{0:.2%}".format(n / series.size))