isnull() in pandas not able to identify blank value (Python coding)

[darpInd]

import pandas as pd
t1=pd.DataFrame()
t1 ['name'] = ["dp","ag","wp"]
t1['status'] = ['a','b','c']
t1['age'] = [10,"",15]
t1
##
print(t1.isnull().values)

Why is the execution of this node not able to identify blank (see "age" column, 2nd row). isnull() is coming false for all the cells, see below output Output:

Output:
 [[False False False] 
 [False False False] 
 [False False False]]