def make_carins_subset(df):
    """Keep observations used for car insurance classification."""
    tagsum = df[['tag', 'auto_tag', 'manual_tag']].sum(1)
    carins_trans = ((tagsum.str.contains('vehicle insurance'))
                    & (df.manual_tag.ne('home insurance')))
    credit = df.amount > 0
    return df[carins_trans & credit]