class_docstr: Modifies the graph by adding a variable.
class_docstr_tok: ["Modifies","the","graph","by","adding","a","variable","."]
code: def __init__(self, var_name="hook_created_variable"):
      self._var_name = var_name
      self._begun = False
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import shutil
  import struct
  import sys
  from absl import flags
  from absl.testing import parameterized
  from adanet import ensemble
  from adanet import subnetwork
  from adanet import tf_compat
  from adanet.core.architecture import _Architecture
  from adanet.core.candidate import _Candidate
  from adanet.core.ensemble_builder import _EnsembleSpec
  from adanet.core.ensemble_builder import _SubnetworkSpec
  from adanet.core.eval_metrics import _EnsembleMetrics
  from adanet.core.eval_metrics import _IterationMetrics
  from adanet.core.eval_metrics import _SubnetworkMetrics
  import tensorflow.compat.v2
label_desc: Use image node_id 1 to create a new ModifierSessionRunHook object from inherited base classes: tf_compat with example: obj = ModifierSessionRunHook(var_name)