code: public static boolean isDetachedPlugin(@Nonnull String pluginId) {
          for (DetachedPlugin detachedPlugin : getDetachedPlugins()) {
              if (detachedPlugin.getShortName().equals(pluginId)) {
                  return true;
              }
          }
  
          return false;
      }
docs: Is the named plugin a plugin that was detached from Jenkins at some point in the past.
  
  @param pluginId The plugin ID.
  @return {@code true} if the plugin is a plugin that was detached from Jenkins at some
  point in the past, otherwise {@code false}.