src/vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads.ts/OutputElement/constructor
class OutputElement:		constructor(
			private readonly outputId: string,
			left: number,
			public readonly cellId: string
		) {
			this.element = document.createElement('div');
			this.element.id = outputId;
			this.element.classList.add('output');
			this.element.style.position = 'absolute';
			this.element.style.top = `0px`;
			this.element.style.left = left + 'px';
			this.element.style.padding = `${ctx.style.outputNodePadding}px ${ctx.style.outputNodePadding}px ${ctx.style.outputNodePadding}px ${ctx.style.outputNodeLeftPadding}`;

			this.element.addEventListener('mouseenter', () => {
				postNotebookMessage<webviewMessages.IMouseEnterMessage>('mouseenter', { id: outputId });
			});
			this.element.addEventListener('mouseleave', () => {
				postNotebookMessage<webviewMessages.IMouseLeaveMessage>('mouseleave', { id: outputId });
			});
		}