code: def email_sender(recipient_emails: list, sender_email: str = None):
      """
      Email sender wrapper: execute func, send an email with the end status
      (sucessfully finished or crashed) at the end. Also send an email before
      executing func.
  
      `recipient_emails`: list[str]
          A list of email addresses to notify.
      `sender_email`: str (default=None)
          The email adress to send the messages. If None, use the same
          address as the first recipient email in `recipient_emails`
          if length of `recipient_emails` is more than 0.
      """
      if sender_email is None and len(recipient_emails) > 0:
          sender_email = recipient_emails[0]
      yag_sender = yagmail.SMTP(sender_email)
  
      def decorator_sender(func):
          @functools.wraps(func)
          def wrapper_sender(*args, **kwargs):
              start_time = datetime.datetime.now()
              host_name = socket.gethostname()
              func_name = func.__name__
  
              # Handling distributed training edge case.
              # In PyTorch, the launch of `torch.distributed.launch` sets up a RANK environment variable for each process.
              # This can be used to detect the master process.
              # See https://github.com/pytorch/pytorch/blob/master/torch/distributed/launch.py#L211
              # Except for errors, only the master process will send notifications.
              if "RANK" in os.environ:
                  master_process = int(os.environ["RANK"]) == 0
                  host_name += " - RANK: %s" % os.environ["RANK"]
              else:
                  master_process = True
  
              if master_process:
                  contents = [
                      "Your training has started.",
                      "Machine name: %s" % host_name,
                      "Main call: %s" % func_name,
                      "Starting date: %s"
                      % start_time.strftime(DATE_FORMAT),
                  ]
                  for i in range(len(recipient_emails)):
                      current_recipient = recipient_emails[i]
                      yag_sender.send(
                          current_recipient,
                          "Training has started 🎬",
                          contents,
                      )
              try:
                  value = func(*args, **kwargs)
  
                  if master_process:
                      end_time = datetime.datetime.now()
                      elapsed_time = end_time - start_time
                      contents = [
                          "Your training is complete.",
                          "Machine name: %s" % host_name,
                          "Main call: %s" % func_name,
                          "Starting date: %s"
                          % start_time.strftime(DATE_FORMAT),
                          "End date: %s"
                          % end_time.strftime(DATE_FORMAT),
                          "Training duration: %s" % str(elapsed_time),
                      ]
  
                      try:
                          str_value = str(value)
                          contents.append(
                              "Main call returned value: %s" % str_value
                          )
                      except:
                          contents.append(
                              "Main call returned value: %s"
                              % "ERROR - Couldn't str the returned value."
                          )
  
                      for i in range(len(recipient_emails)):
                          current_recipient = recipient_emails[i]
                          yag_sender.send(
                              current_recipient,
                              "Training has sucessfully finished 🎉",
                              contents,
                          )
  
                  return value
  
              except Exception as ex:
                  end_time = datetime.datetime.now()
                  elapsed_time = end_time - start_time
                  contents = [
                      "Your training has crashed.",
                      "Machine name: %s" % host_name,
                      "Main call: %s" % func_name,
                      "Starting date: %s"
                      % start_time.strftime(DATE_FORMAT),
                      "Crash date: %s" % end_time.strftime(DATE_FORMAT),
                      "Crashed training duration: %s\n\n"
                      % str(elapsed_time),
                      "Here's the error:",
                      "%s\n\n" % ex,
                      "Traceback:",
                      "%s" % traceback.format_exc(),
                  ]
                  for i in range(len(recipient_emails)):
                      current_recipient = recipient_emails[i]
                      yag_sender.send(
                          current_recipient,
                          "Training has crashed ☠️",
                          contents,
                      )
                  raise ex
  
          return wrapper_sender
  
      return decorator_sender
  
imports: import os
  import datetime
  import traceback
  import functools
  import socket
  import yagmail
label_desc: Use image node_id 1 for calling a global function with example usage: email_sender(recipient_emails, sender_email) and returns: decorator_sender, wrapper_sender, value