import tensorflow as tf

                   .Conv2D('conv1', 20, 5, padding='VALID')
                   .FullyConnected('fc1', out_dim=32)
                   .FullyConnected('fct', out_dim=6, nl=tf.identity,
                                   W_init=tf.constant_initializer(),
                                   b_init=tf.constant_initializer([1, 0, HALF_DIFF, 0, 1, HALF_DIFF]))())
            # output 6 parameters for affine transformation
