Instance normalization layer.

def instance_norm(x):
  """Instance normalization layer."""
  with tf.variable_scope("instance_norm"):
    epsilon = 1e-5
    mean, var = tf.nn.moments(x, [1, 2], keep_dims=True)
    scale = tf.get_variable(
        "scale", [x.get_shape()[-1]],
        initializer=tf.truncated_normal_initializer(mean=1.0, stddev=0.02))
    offset = tf.get_variable(
        "offset", [x.get_shape()[-1]], initializer=tf.constant_initializer(0.0))
    out = scale * tf.div(x - mean, tf.sqrt(var + epsilon)) + offset

    return out