code: func Headers(userAgent string, metaHeaders http.Header) []transport.RequestModifier {
  	modifiers := []transport.RequestModifier{}
  	if userAgent != "" {
  		modifiers = append(modifiers, transport.NewHeaderRequestModifier(http.Header{
  			"User-Agent": []string{userAgent},
  		}))
  	}
  	if metaHeaders != nil {
  		modifiers = append(modifiers, transport.NewHeaderRequestModifier(metaHeaders))
  	}
  	return modifiers
  }
docs: // Headers returns request modifiers with a User-Agent and metaHeaders