How to use the @jupyterlab/rendermime.MimeModel function in @jupyterlab/rendermime

private _updateRenderedInput(): Promise {
    let model = this.model;
    let text = model && model.value.text || DEFAULT_MARKDOWN_TEXT;
    // Do not re-render if the text has not changed.
    if (text !== this._prevText) {
      let mimeModel = new MimeModel({ data: { 'text/markdown': text }});
      if (!this._renderer) {
        this._renderer = this._rendermime.createRenderer('text/markdown');
        this._renderer.addClass(MARKDOWN_OUTPUT_CLASS);
      }
      this._prevText = text;
      return this._renderer.renderModel(mimeModel);
    }
    return Promise.resolve(void 0);
  }

if (this._isRendering) {
      this._renderRequested = true;
      return;
    }

    // Set up for this rendering pass.
    this._renderRequested = false;
    const { context } = this;
    const { model } = context;
    const source = model.toString();
    const data: JSONObject = {};
    // If `hideFrontMatter`is true remove front matter.
    data[MIMETYPE] = this._config.hideFrontMatter
      ? Private.removeFrontMatter(source)
      : source;
    const mimeModel = new MimeModel({
      data,
      metadata: { fragment: this._fragment }
    });

    try {
      // Do the rendering asynchronously.
      this._isRendering = true;
      await this.renderer.renderModel(mimeModel);
      this._isRendering = false;

      // If there is an outstanding request to render, go ahead and render
      if (this._renderRequested) {
        return this._render();
      }
    } catch (reason) {
      // Dispose the document if rendering fails.

private _render(): DocumentRegistry.IReadyWidget {
    let context = this._context;
    let model = context.model;
    let layout = this.layout as PanelLayout;
    let data = { 'text/markdown': model.toString() };
    let mimeModel = new MimeModel({ data, trusted: false });
    let widget = this._rendermime.render(mimeModel);
    if (layout.widgets.length === 2) {
      // The toolbar is layout.widgets[0]
      layout.widgets[1].dispose();
    }
    layout.addWidget(widget);
    return widget;
  }

private _updateRenderedInput(): Promise {
    let model = this.model;
    let text = (model && model.value.text) || DEFAULT_MARKDOWN_TEXT;
    // Do not re-render if the text has not changed.
    if (text !== this._prevText) {
      let mimeModel = new MimeModel({ data: { 'text/markdown': text } });
      if (!this._renderer) {
        this._renderer = this._rendermime.createRenderer('text/markdown');
        this._renderer.addClass(MARKDOWN_OUTPUT_CLASS);
      }
      this._prevText = text;
      return this._renderer.renderModel(mimeModel);
    }
    return Promise.resolve(void 0);
  }

private _updateRenderedInput(): Promise {
    let model = this.model;
    let text = (model && model.value.text) || DEFAULT_MARKDOWN_TEXT;
    // Do not re-render if the text has not changed.
    if (text !== this._prevText) {
      let mimeModel = new MimeModel({ data: { 'text/markdown': text } });
      if (!this._renderer) {
        this._renderer = this._rendermime.createRenderer('text/markdown');
        this._renderer.addClass(MARKDOWN_OUTPUT_CLASS);
      }
      this._prevText = text;
      return this._renderer.renderModel(mimeModel);
    }
    return Promise.resolve(void 0);
  }

private _updateRenderedInput(): Promise {
    let model = this.model;
    let text = (model && model.value.text) || DEFAULT_MARKDOWN_TEXT;
    // Do not re-render if the text has not changed.
    if (text !== this._prevText) {
      let mimeModel = new MimeModel({ data: { 'text/markdown': text } });
      if (!this._renderer) {
        this._renderer = this._rendermime.createRenderer('text/markdown');
        this._renderer.addClass(MARKDOWN_OUTPUT_CLASS);
      }
      this._prevText = text;
      return this._renderer.renderModel(mimeModel);
    }
    return Promise.resolve(void 0);
  }

it('should create a new mime model', () => {
        let model = new MimeModel();
        expect(model).to.be.a(MimeModel);
      });

function createModel(data: JSONObject): IRenderMime.IMimeModel {
  return new MimeModel({ data });
}

function createModel(
  mimeType: string,
  source: JSONValue,
  trusted = false
): IRenderMime.IMimeModel {
  const data: JSONObject = {};
  data[mimeType] = source;
  return new MimeModel({ data, trusted });
}