group data by age and race, calculate the proportion in Python

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
from scipy import stats

da = pd.read_csv("C:/Users/eli/Desktop/YtPruboBEemdqA7UJJ_tgg_63e179e3722f4ef783f58ff6e395feb7_nhanes_2015_2016.csv")

da["agegrp"] = pd.cut(da.RIDAGEYR, [18, 30, 40, 50, 60, 70, 80])
b = da.groupby(["RIAGENDR", "RIDRETH1"]).size().unstack().fillna(0).apply(lambda x: x/x.sum(), axis=1)
print(b)