003 pandas | fillna | Handle missing data

# Handle missing data.
def fill_missing_values(df):
    df.category_name.fillna(value="Other", inplace=True)
    df.brand_name.fillna(value="missing", inplace=True)
    df.item_description.fillna(value="None", inplace=True)
    return df

train_df = fill_missing_values(train_df)
test_df = fill_missing_values(test_df)