def proto_value(self, string):
        """
        String received in the 'value' state.
        """
        self._currentBox[self._currentKey] = string
        self._currentKey = None
        self.MAX_LENGTH = self._MAX_KEY_LENGTH
        return 'key'

        String received in the 'value' state.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/amp.py