code: def _populate_common_request(self, request):
          '''Populate the Request with common fields.'''
          url_record = self._item_session.url_record
  
          # Note that referrer may have already been set by the --referer option
          if url_record.parent_url and not request.fields.get('Referer'):
              self._add_referrer(request, url_record)
  
          if self._fetch_rule.http_login:
              request.username, request.password = self._fetch_rule.http_logif _populate_common_request(self, request):
          '''Populate the Request with common fields.'''
          url_record = self._item_session.url_record
  
          # Note that referrer may have already been set by the --referer option
          if url_record.parent_url and not request.fields.get('Referer'):
              self._add_referrer(request, url_record)
  
          if self._fetch_rule.http_login:
              request.username, request.password = self._fetch_rule.http_login
docs: Populate the Request with common fields.