code: func (p plugins) add(plugin *Plugin) {
  	plugins, ok := p.plugins[plugin.Kind]
  	if !ok {
  		plugins = make([]Plugin, 0)
  	}
  	plugins = append(plugins, *plugin)
  	p.plugins[plugin.Kind] = plugins
  	p.versions[plugin.Name] = plugin.Version
  }
docs: // add adds a plugin to loaded plugin collection.