code: def on_learner_train_start(self, logs):
      self.train_start_time = time.time()
  
file_path: mljar-supervised/supervised/callbacks/total_time_constraint.py
imports: import logging
  import time
  import numpy
  from supervised.callbacks.callback import Callback
  from supervised.exceptions import NotTrainedException
  from supervised.utils.config import LOG_LEVEL
label_desc: Use image node_id 2 for calling the TotalTimeConstraint obj's underlying member method code with example usage: obj.on_learner_train_start(logs) without return types