isinf(0):  False

====================
a:
 array([1.0, 2.0, nan], dtype=float64)

isinf(a):
 array([False, False, False], dtype=bool)

====================
b:
 array([1.0, 2.0, inf], dtype=float64)

isinf(b):
 array([False, False, True], dtype=bool)

====================
c:
 array([1, 2, 3], dtype=uint16)

isinf(c):
 array([False, False, False], dtype=bool)

====================
d:
 array([[inf, nan, nan, nan, nan],
       [nan, inf, nan, nan, nan],
       [nan, nan, inf, nan, nan],
       [nan, nan, nan, inf, nan],
       [nan, nan, nan, nan, inf]], dtype=float64)

isinf(d):
 array([[True, False, False, False, False],
       [False, True, False, False, False],
       [False, False, True, False, False],
       [False, False, False, True, False],
       [False, False, False, False, True]], dtype=bool)