private static List<String> validateTag(String tag) {
    if (tag == null) {
      return getMutableSingletonList("Tag can't be null");
    }

    if (tag.length() > MAX_TAG_LENGTH) {
      return getMutableSingletonList("Tag must be shorter than " + MAX_TAG_LENGTH);
    }

    return null;
  }
Attempts to validate the provided RetryStrategy. If valid, null is returned. Otherwise a list
of errors will be returned.
jobdispatcher/src/main/java/com/firebase/jobdispatcher/DefaultJobValidator.java