code: public Plugin stopPlugin(final String pluginName) {
          synchronized (pluginMap) {
              Plugin plugin = (Plugin) pluginMap.get(pluginName);
  
              if (plugin == null) {
                  return null;
              }
  
              // shutdown the plugin
              plugin.shutdown();
  
              // remove it from the plugin map
              pluginMap.remove(pluginName);
              firePluginStopped(plugin);
  
              // return it for future use
              return plugin;
          }
      }
docs: Stops a plugin by plugin name and repository.
  
  @param pluginName the name of the plugin to stop.
  @return Plugin the plugin, if stopped, or null if the
  the plugin was not found in the registry.