Adds a local response normalization layer.

def lrn(self, depth_radius, bias, alpha, beta):
        """Adds a local response normalization layer."""
        name = "lrn" + str(self.counts["lrn"])
        self.counts["lrn"] += 1
        self.top_layer = tf.nn.lrn(
            self.top_layer, depth_radius, bias, alpha, beta, name=name)
        return self.top_layer