get previewItem() {
      if (!this._previewItem) {
        return null;
      }
      return this.getSuggestionByListItem(this._previewItem);
    }
The suggestion item on preview.
@type {sap.ui.webc.main.IInputSuggestionItem | null}
@name sap.ui.webc.main.Input.prototype.previewItem
@readonly
@public