What does the "use_dilated" mean in "build" function?

[VincentFEI]

I can't understand what codes below want to do, does anybody can explain?
Thanks so much !!!

if use_dilated:
    pad = [[0, 0], [0, 0]]
    self.pool4 = tf.nn.max_pool(self.conv4_3, ksize=[1, 2, 2, 1],
                                strides=[1, 1, 1, 1],
                                padding='SAME', name='pool4')
    self.pool4 = tf.space_to_batch(self.pool4,
                                   paddings=pad, block_size=2)
else:
    self.pool4 = self._max_pool(self.conv4_3, 'pool4', debug)

[MarvinTeichmann]

This implements dilated (atrous) convolutions.