code: def send_fragment_start(self, data):
          
          opcode = BINARY
          if _check_unicode(data):
              opcode = TEXT
  
          self._send_message(True, opcode, data)
docs: Send the start of a data fragment stream to a websocket client.
              Subsequent data should be sent using sendFragment().
              A fragment stream is completed when sendFragmentEnd() is called.
  
              If data is a unicode object then the frame is sent as Text.
              If the data is a bytearray object then the frame is sent as Binary.