class_docstr: Send a notification to a channel at the beginning/ending of the training/testing and at a constant frequency
  (`alert_frequency`) during the training.
  
  Args:
      notificator (~poutyne.Notificator): The notification channel to send the message.
          The expected interface need to implement a `send_notification` method to send the message. You can see the
          `notif <https://notificationdoc.ca/index.html>`_ package which implements some Notificator respecting the
          interface.
      alert_frequency (int): The frequency (in epoch), during training, to send an update. By default, 1.
      experiment_name (Union[str, None]): The name of the experiment to add to the message. By default, None.
  
  Example:
  
      .. code-block:: python
  
          from notif.notificator import SlackNotificator
          from poutyne.framework.callbacks.notification import NotificationCallback
  
          webhook_url = "a_link"
          slack_notif = SlackNotificator(webhook_url=webhook_url)
  
          notif_callback = NotificationCallback(notificator=slack_notif)
  
          model = Model(...)
          model.fit_generator(..., callbacks=[notif_callback])
docstr: Send the message to the channel 'Start of the training' or
  'Start of the training for the experiment experiment_name' if an experiment name is given.
docstr_tok: ["Send","the","message","to","the","channel","'Start","of","the","training","'","or","'Start","of","the","training","for","the","experiment","experiment_name","'","if","an","experiment","name","is","given","."]
code: def on_train_begin(self, logs: Dict) -> None:
      """
      Send the message to the channel 'Start of the training' or
      'Start of the training for the experiment experiment_name' if an experiment name is given.
      """
      empty_message = ""
      self.notificator.send_notification(
          empty_message,
          subject=f"Start of the training{self.experiment_name_msg}.",
      )
  
file_path: poutyne/poutyne/framework/callbacks/notification.py
imports: from abc import ABC, abstractmethod
  from typing import Dict, Union
  from poutyne.framework.callbacks.callbacks import Callback
label_desc: Use image node_id 2 for calling the NotificationCallback obj's underlying member method code with example usage: obj.on_train_begin(logs) without return types