Checking Null values in Groupby

import numpy as np
import pandas as pd
pd.options.display.width = 1000

df = pd.DataFrame(
    {'shop': [101, 101, 101, 102, 102, 102, 103, 103, 103, 103],
     'price': [75, 150, 300, 300, 600, 600, 1000, 1000, np.nan, np.nan]})

grouped = df.groupby('shop')['price']
print(type(grouped))

df['has_null'] = grouped.transform(lambda x: pd.isnull(x).any()).astype(bool)

df