code: func (c *Conn) Categories(nick string) ([]*Category, error) {
  	var out struct {
  		Categories []*Category
  	}
  	if err := c.do("smugmug.categories.get", &out, "NickName", nick); err != nil {
  		return nil, err
  	}
  	return out.Categories, nil
  }
docs: // Categories returns the album categories for the user identified by the nick name.