src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts/OutputFocusTracker/dispose
class OutputFocusTracker:		dispose() {
			if (this._element) {
				this._element.removeEventListener('focus', this._onFocus, true);
				this._element.removeEventListener('blur', this._onBlur, true);
			}
		}