@Override protected RelNode visitChild(RelNode parent, int i,
                                           RelNode input) {
      return super.visitChild(parent, i, stripHep(input));
    }
Creates a CorelMap by iterating over a {@link RelNode} tree.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelDecorrelator.java