There is a Pandas dataframe: userId movieId rating timestamp 0 1 31 2.5 1260759144 1 1 1029 3.0 1260759179 2 1 1061 3.0 1260759182 3 1 1129 2.0 1260759185 4 1 1172 4.0 1260759205 Group the data by "userId" column and output in a separate column the number of values in the "rating" column

def groupby_cnt(df):
    df = pd.DataFrame(df.groupby("userId")["rating"].count())
    df.columns = ['ratings_cnt']
    return df