code: func (b *SearchRequestBuilder) SortDesc(field, unmappedType string) *SearchRequestBuilder {
  	props := map[string]string{
  		"order": "desc",
  	}
  
  	if unmappedType != "" {
  		props["unmapped_type"] = unmappedType
  	}
  
  	b.sort[field] = props
  
  	return b
  }
docs: // SortDesc adds a sort to the search request