code: def _get_reader(self, network_reader):
          
          with (yield from self._lock):
              if self._reader_process is None:
                  self._reader_process = network_reader
              if self._reader:
                  if self._reader_process == network_reader:
                      self._current_read = asyncio.async(self._reader.read(READ_SIZE))
                      return self._current_read
          return None
docs: Get a reader or None if another reader is already reading.