docs: public static Exemplar create(
        double value, Timestamp timestamp, Map<String, AttachmentValue> attachments) {
      checkNotNull(attachments, "attachments");
      Map<String, AttachmentValue> attachmentsCopy =
          Collections.unmodifiableMap(new HashMap<String, AttachmentValue>(attachments));
      for (Entry<String, AttachmentValue> entry : attachmentsCopy.entrySet()) {
        checkNotNull(entry.getKey(), "key of attachments");
        checkNotNull(entry.getValue(), "value of attachments");
      }
      return new AutoValue_Exemplar(value, timestamp, attachmentsCopy);
    }