src/vs/workbench/browser/parts/notifications/notificationsViewer.ts/NotificationTemplateRenderer/renderSeverity
class NotificationTemplateRenderer:	private renderSeverity(notification: INotificationViewItem): void {
		// first remove, then set as the codicon class names overlap
		NotificationTemplateRenderer.SEVERITIES.forEach(severity => {
			if (notification.severity !== severity) {
				this.template.icon.classList.remove(...this.toSeverityIcon(severity).classNamesArray);
			}
		});
		this.template.icon.classList.add(...this.toSeverityIcon(notification.severity).classNamesArray);
	}