code: public function getThemeLocator()
      {
          if (! $this->themeLocator) {
              // use default theme locator to resolve theme object
              /** @var $defaultThemeLocator \yimaTheme\Theme\Locator */
              $defaultThemeLocator = $this->sm->get('yimaTheme.ThemeLocator');
              if (!$defaultThemeLocator instanceof LocatorDefaultInterface) {
                  throw new \Exception(
                      'Default Theme Locator Service (yimaTheme.ThemeLocator) must instance of yimaTheme\Theme\LocatorDefaultInterface'
                  );
              }
              $this->themeLocator = $defaultThemeLocator;
          }
  
          return $this->themeLocator;
      }
docs: Get ThemeLocator
  
  @throws \Exception
  @return LocatorDefaultInterface