@Nullable
  private static List<String> validateForPersistence(@Nullable Bundle extras) {
    List<String> errors = null;

    if (extras != null) {
      // check the types to make sure they're persistable
      for (String k : extras.keySet()) {
        errors = addError(errors, validateExtrasType(extras, k));
      }
    }

    return errors;
  }
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