old_contents: from django.contrib import messages
  from django.core.mail import send_mail
  from django.utils.translation import ugettext_lazy as _
  
  import stored_messages
  
  from osmaxx.excerptexport import models
  
  
  class ConverterHelper:
      def __init__(self, extraction_order):
          self.extraction_order = extraction_order
          self.user = extraction_order.orderer
  
      def file_conversion_finished(self):
          if self.extraction_order.output_files.count() >= len(self.extraction_order.extraction_formats):
              self.inform_user(
                  messages.SUCCESS,
                  _('The extraction of the order "%(order_id)s" has been finished.') % {
                      'order_id': self.extraction_order.id
                  },
                  email=True
              )
              self.extraction_order.state = models.ExtractionOrderState.FINISHED
              self.extraction_order.save()
  
      def inform_user(self, message_type, message_text, email=True):
          stored_messages.api.add_message_for(
              users=[self.user],
              level=message_type,
              message_text=message_text
          )
  
          if email:
              if hasattr(self.user, 'email'):
                  send_mail(
                      '[OSMAXX] '+message_text,
                      message_text,
                      'no-reply@osmaxx.hsr.ch',
                      [self.user.email]
                  )
              else:
                  self.inform_user(
                      messages.WARNING,
                      _("There is no email address assigned to your account. "
                        "You won't be notified by email on process finish!"),
                      email=False
                  )
  
new_contents: from django.contrib import messages
  from django.core.mail import send_mail
  from django.utils.translation import ugettext_lazy as _
  
  import stored_messages
  
  from osmaxx.excerptexport import models
  
  
  # functions using database (extraction_order) must be instance methods of a class
  # -> free functions will not work: database connection error
  class ConverterHelper:
      def __init__(self, extraction_order):
          self.extraction_order = extraction_order
          self.user = extraction_order.orderer
  
      def file_conversion_finished(self):
          if self.extraction_order.output_files.count() >= len(self.extraction_order.extraction_formats):
              self.inform_user(
                  messages.SUCCESS,
                  _('The extraction of the order "%(order_id)s" has been finished.') % {
                      'order_id': self.extraction_order.id
                  },
                  email=True
              )
              self.extraction_order.state = models.ExtractionOrderState.FINISHED
              self.extraction_order.save()
  
      def inform_user(self, message_type, message_text, email=True):
          stored_messages.api.add_message_for(
              users=[self.user],
              level=message_type,
              message_text=message_text
          )
  
          if email:
              if hasattr(self.user, 'email'):
                  send_mail(
                      '[OSMAXX] '+message_text,
                      message_text,
                      'no-reply@osmaxx.hsr.ch',
                      [self.user.email]
                  )
              else:
                  self.inform_user(
                      messages.WARNING,
                      _("There is no email address assigned to your account. "
                        "You won't be notified by email on process finish!"),
                      email=False
                  )
  
subject: Document reason for class instead of free function