th> a = torch.ones(3,2,2)
th> b = nn.SpatialZeroPadding(0, 0, 1)(a)
th> b

(1,.,.) =
0 0
1 1
1 1

(2,.,.) =
0 0
1 1
1 1

(3,.,.) =
0 0
1 1
1 1

th> b = nn.SpatialZeroPadding(0, 0, 2)(a)   
th> b

(1,.,.) =
0 0
0 0
1 1
1 1

(2,.,.) =
0 0
0 0
1 1
1 1

(3,.,.) =
0 0
0 0
1 1
1 1

th> b = nn.SpatialZeroPadding(0, 1, 0)(a)
th> b

(1,.,.) =
1 1 0
1 1 0

(2,.,.) =
1 1 0
1 1 0

(3,.,.) =
1 1 0
1 1 0

th> b = nn.SpatialZeroPadding(1, 0, 0)(a)
th> b

(1,.,.) =
0 1 1
0 1 1
0 0 0

(2,.,.) =
0 1 1
0 1 1
0 0 0

(3,.,.) =
0 1 1
0 1 1
0 0 0