public Object getField(Object o) {
    if (o == null) {
      return null;
    }
    LazyBinaryUnion lazyBinaryUnion = (LazyBinaryUnion) o;
    return lazyBinaryUnion.getField();
  }
Return the field based on the tag value associated with the Object.
serde/src/java/org/apache/hadoop/hive/serde2/lazybinary/objectinspector/LazyBinaryUnionObjectInspector.java