src/vs/workbench/contrib/notebook/browser/viewParts/notebookEditorDecorations.ts/NotebookDecorationCSSRules/_buildCSS
class NotebookDecorationCSSRules:	private _buildCSS() {
		if (this._providerArgs.options.backgroundColor) {
			const backgroundColor = this._resolveValue(this._providerArgs.options.backgroundColor);
			this._styleSheet.insertRule(`.monaco-workbench .notebookOverlay .monaco-list .monaco-list-row.code-cell-row.${this.className} .cell-focus-indicator,
			.monaco-workbench .notebookOverlay .monaco-list .monaco-list-row.markdown-cell-row.${this.className} {
				background-color: ${backgroundColor} !important;
			}`);
		}

		if (this._providerArgs.options.borderColor) {
			const borderColor = this._resolveValue(this._providerArgs.options.borderColor);

			this._styleSheet.insertRule(`.monaco-workbench .notebookOverlay .monaco-list .monaco-list-row.${this.className} .cell-focus-indicator-top:before,
					.monaco-workbench .notebookOverlay .monaco-list .monaco-list-row.${this.className} .cell-focus-indicator-bottom:before {
						border-color: ${borderColor} !important;
					}`);

			this._styleSheet.insertRule(`
					.monaco-workbench .notebookOverlay .monaco-list .monaco-list-row.${this.className} .cell-focus-indicator-bottom:before {
						content: "";
						position: absolute;
						width: 100%;
						height: 1px;
						border-bottom: 1px solid ${borderColor};
						bottom: 0px;
					`);

			this._styleSheet.insertRule(`
					.monaco-workbench .notebookOverlay .monaco-list .monaco-list-row.${this.className} .cell-focus-indicator-top:before {
						content: "";
						position: absolute;
						width: 100%;
						height: 1px;
						border-top: 1px solid ${borderColor};
					`);

			// more specific rule for `.focused` can override existing rules
			this._styleSheet.insertRule(`.monaco-workbench .notebookOverlay .monaco-list:focus-within .monaco-list-row.focused.${this.className} .cell-focus-indicator-top:before,
				.monaco-workbench .notebookOverlay .monaco-list:focus-within .monaco-list-row.focused.${this.className} .cell-focus-indicator-bottom:before {
					border-color: ${borderColor} !important;
				}`);
		}

		if (this._providerArgs.options.top) {
			const unthemedCSS = this._getCSSTextForModelDecorationContentClassName(this._providerArgs.options.top);
			this._styleSheet.insertRule(`.monaco-workbench .notebookOverlay .monaco-list .monaco-list-row.${this.className} .cell-decoration .${this.topClassName} {
				height: 1rem;
				display: block;
			}`);

			this._styleSheet.insertRule(`.monaco-workbench .notebookOverlay .monaco-list .monaco-list-row.${this.className} .cell-decoration .${this.topClassName}::before {
				display: block;
				${unthemedCSS}
			}`);
		}
	}