code: func (l *List) String() string {
  	l.key.RLock()
  	defer l.key.RUnlock()
  
  	builder := bytes.NewBufferString("[")
  
  	for i, entry := range l.underlyer {
  		if i >= 15 {
  			builder.WriteString("... ")
  			break
  		}
  		builder.WriteString(fmt.Sprintf("%v ", entry))
  	}
  	builder.Truncate(builder.Len() - 1)
  	builder.WriteRune(']')
  	return builder.String()
  }
docs: // String generates a textual representation of the List for the sake of debugging.