code: def unpack(cls, msg):
          
          # PYTHON-945: ignore starting_from field.
          flags, cursor_id, _, number_returned = cls.UNPACK_FROM(msg)
  
          # Convert Python 3 memoryview to bytes. Note we should call
          # memoryview.tobytes() if we start using memoryview in Python 2.7.
          documents = bytes(msg[20:])
          return cls(flags, cursor_id, number_returned, documents)
docs: Construct an _OpReply from raw bytes.