class_docstr: FileWriter for test.
  
  TensorFlow FileWriter uses TensorFlow's Protobuf Python binding
  which is largely discouraged in TensorBoard. We do not want a
  TB.Writer but require one for testing in integrational style
  (writing out event files and use the real event readers).
code: def add_graph(self, graph, global_step=None, graph_def=None):
      if isinstance(graph_def, graph_pb2.GraphDef):
          tf_graph_def = tf.compat.v1.GraphDef.FromString(
              graph_def.SerializeToString()
          )
      else:
          tf_graph_def = graph_def
  
      super().add_graph(
          graph, global_step=global_step, graph_def=tf_graph_def
      )
  
imports: import threading
  import tensorflow
  from tensorboard.compat.proto import event_pb2
  from tensorboard.compat.proto import graph_pb2
  from tensorboard.compat.proto import meta_graph_pb2
  from tensorboard.compat.proto import summary_pb2
  from tensorboard.util import tb_logging
label_desc: Use image node_id 6 for calling the FileWriter obj's underlying member method code with example usage: obj.add_graph(graph, global_step, graph_def) without return types