def gby_count(df, col, col_full_name=False):
    """
    Perform groupby count aggregation, rename column to count,
    and keep flat structure of DataFrame.
    Wrapper on pd.DataFrame.groupby
    """
    if col_full_name:
        col_name = "count_" + col
    else:
        col_name = "count"
    return df.groupby(col).size().reset_index(name=col_name).sort_values(by=col_name, ascending=False)