src/vs/editor/browser/services/abstractCodeEditorService.ts/CSSNameHelper/getSelector
class CSSNameHelper:	public static getSelector(key: string, parentKey: string | undefined, ruleType: ModelDecorationCSSRuleType): string {
		let selector = '.monaco-editor .' + this.getClassName(key, ruleType);
		if (parentKey) {
			selector = selector + '.' + this.getClassName(parentKey, ruleType);
		}
		if (ruleType === ModelDecorationCSSRuleType.BeforeContentClassName) {
			selector += '::before';
		} else if (ruleType === ModelDecorationCSSRuleType.AfterContentClassName) {
			selector += '::after';
		}
		return selector;
	}