docs: def start_transfer(self):
          ''' pass the transfer spec to the Aspera sdk and start the transfer '''
          try:
              if not self.is_done():
                  faspmanager2.startTransfer(self.get_transfer_id(),
                                             None,
                                             self.get_transfer_spec(),
                                             self)
          except Exception as ex:
              self.notify_exception(ex)