code: def on_train_batch_begin(self, batch, logs=None):
      if batch == self.start_batch:
          self.state["epoch_begin_time"] = time.time()
  
imports: import time
  import keras
label_desc: Use image node_id 2 for calling the BenchmarkMetricsCallback obj's underlying member method code with example usage: obj.on_train_batch_begin(batch, logs) without return types