code: func (mem *memNamedMapping) ListFields(name string) map[string][]string {
  	mem.access.RLock()
  	defer mem.access.RUnlock()
  
  	fields := make(map[string][]string)
  
  	item, found := mem.nameToIdx[name]
  	if found {
  		for field := range item.indexed {
  			fields[field] = []string{}
  			for _, value := range item.indexed[field] {
  				fields[field] = append(fields[field], value)
  			}
  		}
  	}
  
  	return fields
  }
docs: // ListFields returns a map of fields (secondary indexes) and their values
  // currently associated with the item identified by <name>.