How do you implement save() and load() for TradingView's Charting Library

I can confirm that save() and load() are working without issue on my project. It took a bit of fussing with Types to get it working. I am sure someone will look at this pile and despair - but it works.

So for anyone else that wants to test:

tvWidget.load(savedObject)
tvWidget.save((saveObject) => this.chartService.saveCurrentChart(saveObject))

I created a save button in the tvWidget header:

    const saveButton = tvWidget.createButton();
    saveButton.setAttribute('title', 'Click to Save Chart');
    saveButton.classList.add('apply-common-tooltip');
    saveButton.addEventListener('click', () => tvWidget.save((saveObject) => this.chartService.saveCurrentChart(saveObject, tvWidget)))
    saveButton.innerHTML = 'Save Chart';

And a Load Button in the tvWidget header:

    createDrawingButton(tvWidget: IChartingLibraryWidget) {
    const loadButton = tvWidget.createButton();
    loadButton.setAttribute('title', 'Click to Load Chart');
    loadButton.classList.add('apply-common-tooltip');
    loadButton.addEventListener('click', () => tvWidget.load(this.chartService.loadSavedChart()));
    loadButton.innerHTML = 'Load from Backend';

Here is my TypeScript Interface:

export interface APIChartData {
    ltChartId?: number | undefined
        tvChartId?: string | undefined
    chartObject: Object
        lastUpdate?: number | undefined
}

Here is my Save Function:

saveCurrentChart(tvChartObject: any) {

let chartID = tvChartObject['charts'][0]['panes'][0]['sources'][0]['id'];
let chartToSave: APIChartData = {
      ltChartId: this._currentChart?.ltChartId,
      tvChartId: chartID,
      chartObject: tvChartObject,
      lastUpdate: Math.floor(Date.now() / 1000),
    };

    this.postChart(chartToSave).subscribe((response) => {

      console.log("Response from Server")
      console.log(response.ltChartId)
      this._savedChartId =  response.ltChartId
    });

    console.log(`Saved Chart Object`);
  }

private postChart(saveChart: APIChartData): Observable<ChartStoreResponse> {
    console.log('Trying to save...');
    const httpOptions = {
      headers: new HttpHeaders({
        'Content-Type': 'application/json',
        accept: 'application/json',
        Authorization: this._oAuthTokent,
      }),
    };

Here is my Load Function:

loadSavedChart(chartID:number = this._savedChartId): Object {

    console.log('Trying to load...');
    const httpOptions = {
      headers: new HttpHeaders({
        'Content-Type': 'application/json',
        accept: 'application/json',
        Authorization: this._oAuthTokent,
      }),

      params: new HttpParams().set('chart', chartID.toString()),
    };

    const httpParams = {};

    // My "Backend" in a docker image locally running FASTAPI
    const LoadURL = 'http://localhost/api/v1/tradingview';

    let chartObject: Object = {};

    let loadChart$ = this.http
      .get<APIChartData>(LoadURL, httpOptions)
      .pipe(tap(() => console.log('Loaded the goods.')));

    loadChart$.subscribe((object) => {

      this._chartFromDisk = object.chartObject;
      console.log(`Chart ${chartID} from Server Store:`)
      console.log(object.chartObject);

    });

    return this._chartFromDisk;
  }