def get_null_stats(df):
    """
    Function that will return count (absolute and relative)  of null 
    values in each column in `df`.

    Parameters
    ----------

    df : pandas.DataFrame
        DataFrame on which this function will operate.

    Return
    ------

    pandas.DataFrame with `df.columns` as row index and `["cnt", "ratio"]` 
    (for absolute and relative counts, respectively) in column index.
    """
    nulls = df.isnull().sum()
    nulls = nulls.rename("cnt").to_frame()
    nulls["ratio"] = nulls / len(df)
    return nulls.sort_values("ratio", ascending=False)