code: def _tobytes(self):
          
          if not self._has_view:
              # fast path optimization
              if len(self._deque) == 0:
                  return b""
              elif len(self._deque) == 1:
                  # no copy
                  return self._deque[0]
              else:
                  return b"".join(self._deque)
          else:
              tmp = [x.tobytes() if isinstance(x, memoryview) else x
                     for x in self._deque]
              return b"".join(tmp)
docs: Serializes the write buffer into a single string (bytes).
  
          Returns:
              a string (bytes) object.