public static StandardUnionObjectInspector getStandardUnionObjectInspector(
      List<ObjectInspector> unionObjectInspectors) {
    StandardUnionObjectInspector result = cachedStandardUnionObjectInspector.asMap()
        .get(unionObjectInspectors);
    if (result == null) {
      result = new StandardUnionObjectInspector(unionObjectInspectors);
      StandardUnionObjectInspector prev =
        cachedStandardUnionObjectInspector.asMap().putIfAbsent(unionObjectInspectors, result);
      if (prev != null) {
        result = prev;
      }
    }
    return result;
  }
Verify that we don't have an unexpected type of object inspector.
@param option The option to verify
@param oi The ObjectInspector to verify
@param checkOption We're only interested in this option type
@param classes ObjectInspector should not be of these types
serde/src/java/org/apache/hadoop/hive/serde2/objectinspector/ObjectInspectorFactory.java