clear() {
    this.itemLookup = {};
    this.items = [];
    this.responseLookup = {};
    this.responses = [];
    this.queuedSpeechItems = {};
    this.queuedTranscriptItems = {};
    this.queuedInputAudio = null;
    return true;
  }
Clears the conversation history and resets to default
@returns {true}