'String received in the \'key\' state.  If the key is empty, a complete
box has been received.'

def proto_key(self, string):

    if string:
        self._currentKey = string
        self.MAX_LENGTH = self._MAX_VALUE_LENGTH
        return 'value'
    else:
        self.boxReceiver.ampBoxReceived(self._currentBox)
        self._currentBox = None
        return 'init'
