@Override
    public Optional<SpaceViolationPolicy> getPolicy() {
      return policy;
    }
Returns the violation policy, which may be null. It is guaranteed to be non-null if
{@link #isInViolation()} is {@code true}, but may be null otherwise.
hbase-client/src/main/java/org/apache/hadoop/hbase/quotas/SpaceQuotaSnapshot.java