code: func (c *Client) Plugins() ([]string, error) {
  	stats, err := c.ClusterStats().Do(context.Background())
  	if err != nil {
  		return nil, err
  	}
  	if stats == nil {
  		return nil, err
  	}
  	if stats.Nodes == nil {
  		return nil, err
  	}
  	var plugins []string
  	for _, plugin := range stats.Nodes.Plugins {
  		plugins = append(plugins, plugin.Name)
  	}
  	return plugins, nil
  }
docs: // Plugins returns the list of all registered plugins.