old_contents: def get_referrer_from_request(request):
      # determine what source led the user to the export directory
      # if navigating internally then return None
      return 'aaa'
  
new_contents: def get_referrer_from_request(request):
      # TODO: determine what source led the user to the export directory
      # if navigating internally then return None (ticket ED-138)
      return 'aaa'
  
subject: Add TODO to comment in registration helper to reduce risk of task being forgotten