DataFrame 结构的数据 df，按照列名 key1 对数据 df 的各列求最大值
df = pd.DataFrame({'key1':['a', 'c', 'b', 'a', 'b','b','c','a','b','c'],
'key2':['one', 'three', 'two', 'two', 'one','three','three','two','one','one'],
'data':np.random.randint(1,10,size=10)})
grouped = df. ______("key1")
grouped. ______()
groupby max