docs: def _data_channel_close(self, channel, transmit=True):
          """
          Request closing the datachannel by sending an Outgoing Stream Reset Request.
          """
          if channel.readyState not in ['closing', 'closed']:
              channel._setReadyState('closing')
              self._reconfig_queue.append(channel.id)
              if len(self._reconfig_queue) == 1:
                  asyncio.ensure_future(self._transmit_reconfig())