class_docstr: Callback for Keras models.
code: def on_batch_begin(self, batch, logs=None):
      self.global_steps += 1
      if self.global_steps == 1:
          self.start_time = time.time()
          self.timestamp_log.append(
              BatchTimestamp(self.global_steps, self.start_time)
          )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import time
  import tensorflow
  from tensorflow.core.protobuf import rewriter_config_pb2
  from tensorflow.python import tf2
  from tensorflow.python.eager import profiler
label_desc: Use image node_id 4 for calling the TimeHistory obj's underlying member method code with example usage: obj.on_batch_begin(batch, logs) without return types