code: def build_graph(self, input1, input2):
      cost = tf.identity(input1 - input2, name="total_costs")
      summary.add_moving_summary(cost)
      return cost
  
file_path: tensorpack/examples/boilerplate.py
imports: import argparse
  import os
  import tensorflow
  from tensorpack import *
label_desc: Use image node_id 2 for calling the Model obj's underlying member method code with example usage: obj.build_graph(input1, input2) and returns: cost