code: func (c *Conn) Validate(index string, _type string, args map[string]interface{}) (BaseResponse, error) {
  	var url string
  	var retval BaseResponse
  	if len(_type) > 0 {
  		url = fmt.Sprintf("/%s/%s/_validate/", index, _type)
  	} else {
  		url = fmt.Sprintf("/%s/_validate/", index)
  	}
  	body, err := c.DoCommand("GET", url, args, nil)
  	if err != nil {
  		return retval, err
  	}
  	if err == nil {
  		// marshall into json
  		jsonErr := json.Unmarshal(body, &retval)
  		if jsonErr != nil {
  			return retval, jsonErr
  		}
  	}
  	return retval, err
  }
docs: // Validate allows a user to validate a potentially expensive query without executing it.
  // see http://www.elasticsearch.org/guide/reference/api/validate.html