code: def optimizer(self):
      lr = tf.get_variable(
          "learning_rate", initializer=1e-2, trainable=False
      )
      tf.summary.scalar("lr", lr)
      return tf.train.AdamOptimizer(lr, epsilon=1e-3)
  
file_path: tensorpack/examples/basics/cifar-convnet.py
imports: import argparse
  import os
  from tensorpack import tfv1
  from tensorpack import *
  from tensorpack.dataflow import dataset
  from tensorpack.tfutils.summary import *
  from tensorpack.utils.gpu import get_num_gpu
label_desc: Use image node_id 4 for calling the Model obj's underlying member method code with example usage: obj.optimizer() and returns: tf