code: func (fsc *FetchSourceContext) Query() url.Values {
  	params := url.Values{}
  	if fsc.fetchSource {
  		if len(fsc.includes) > 0 {
  			params.Add("_source_includes", strings.Join(fsc.includes, ","))
  		}
  		if len(fsc.excludes) > 0 {
  			params.Add("_source_excludes", strings.Join(fsc.excludes, ","))
  		}
  	} else {
  		params.Add("_source", "false")
  	}
  	return params
  }
docs: // Query returns the parameters in a form suitable for a URL query string.