docs: def cancel(self):
          """Cancel the current transfer.
  
          :rtype: ``bool``
          """
  
          method, url = get_URL('cancel')
  
          payload = {
              'apikey': self.config.get('apikey'),
              'transferid': self.transfer_id,
              'transferkey': self.transfer_info.get('transferkey')
              }
  
          res = getattr(self.session, method)(url, params=payload)
  
          if res.status_code == 200:
              self._complete = True
              return True
  
          hellraiser(res)