code: public PluginComponentCache components(long pluginId)
      {
          PluginComponentCache cache = components.get(pluginId);
          if(cache == null)
              components.put(pluginId, cache = new PluginComponentCache(pluginId));
          return cache;
      }
docs: Returns the cache of plugin components for the given plugin, creating one if it doesn't exist .
  @param pluginId The id of the plugin for the cache of plugin component
  @return The cache of plugin components for the given plugin