class_docstr: Prints summary statistics of all tf variables.
class_docstr_tok: ["Prints","summary","statistics","of","all","tf","variables","."]
code: def before_run(self, _):
      return tf.train.SessionRunArgs(self._fetches)
  
imports: import os
  import time
  from absl import logging
  from magenta.models.gansynth.lib import networks
  import numpy
  import tensorflow.compat.v1
  import tensorflow_gan
label_desc: Use image node_id 2 for calling the ProganDebugHook obj's underlying member method code with example usage: obj.before_run(_) and returns: tf