def layer_op(self, inputs):
spatial_rank = layer_util.infer_spatial_rank(inputs)
kernel_shape = np.hstack((
[self.border * 2 + 1] * spatial_rank, 1, 1)).flatten()
// initializer a kernel with all 0s, and set the central element to 1
np_kernel = layer_util.trivial_kernel(kernel_shape)
crop_kernel = tf.constant(np_kernel, dtype=inputs.dtype)
// split channel dim
output_tensor = [tf.expand_dims(x, -1)
for x in tf.unstack(inputs, axis=-1)]
output_tensor = [tf.nn.convolution(input=inputs,