@Nullable
  private static List<String> mergeErrorLists(
      @Nullable List<String> errors, @Nullable List<String> newErrors) {
    if (errors == null) {
      return newErrors;
    }
    if (newErrors == null) {
      return errors;
    }

    errors.addAll(newErrors);
    return errors;
  }
Combines two {@literal List<String>s} together.
jobdispatcher/src/main/java/com/firebase/jobdispatcher/DefaultJobValidator.java