old_contents: from django.conf import settings
  from django.core.mail import send_mass_mail
  from django.template.loader import render_to_string
  from django.utils.translation import ugettext_lazy as _
  from pigeon.notification import Notification
  
  
  def send_emails(notification):
      messages = []
      context = {'site': notification.site}
      for user in notification.users:
          message = render_to_string(notification.template_name, context)
          messages.append([
              notification.subject,
              message,
              settings.DEFAULT_FROM_EMAIL,
              [user.email],
          ])
      send_mass_mail(messages)
  
  
  class AccountInactiveNotification(Notification):
      handlers = (send_emails,)
      template_name = 'user_deletion/email_notification.txt'
      subject = _('Re-activate your account')
  
  
  class AccountDeletedNotification(Notification):
      handlers = (send_emails,)
      template_name = 'user_deletion/email_deletion.txt'
      subject = _('Your account has been deleted')
  
new_contents: from django.conf import settings
  from django.core.mail import send_mass_mail
  from django.template.loader import render_to_string
  from django.utils.translation import ugettext_lazy as _
  from pigeon.notification import Notification
  
  
  def build_emails(notification):
      context = {'site': notification.site}
      for user in notification.users:
          message = render_to_string(notification.template_name, context)
          yield [
              notification.subject,
              message,
              settings.DEFAULT_FROM_EMAIL,
              [user.email],
          ]
  
  
  def send_emails(notification):
      messages = build_emails(notification)
      send_mass_mail(messages)
  
  
  class AccountInactiveNotification(Notification):
      handlers = (send_emails,)
      template_name = 'user_deletion/email_notification.txt'
      subject = _('Re-activate your account')
  
  
  class AccountDeletedNotification(Notification):
      handlers = (send_emails,)
      template_name = 'user_deletion/email_deletion.txt'
      subject = _('Your account has been deleted')
  
subject: Use a generator instead of append