private boolean isParentMap() {
    return currentLevel >= 2 &&
        currentComplexTypeHelpers[currentLevel - 2] instanceof MapComplexTypeHelper;
  }
Parse the byte[] and fill each field.

This is an adapted version of the parse method in the LazyStruct class.
They should parse things the same way.
serde/src/java/org/apache/hadoop/hive/serde2/lazy/fast/LazySimpleDeserializeRead.java