public PTFDesc getPtfDesc() {
    return ptfDesc;
  }
This method is invoked during runtime(during deserialization of theQueryDef).
At this point the TableFunction can assume that the {@link ExprNodeDesc Expression Nodes}
exist for all the Def (ArgDef, ColumnDef, WindowDef..). It is the responsibility of
the TableFunction to construct the {@link ExprNodeEvaluator evaluators} and setup the OI.

@throws HiveException
ql/src/java/org/apache/hadoop/hive/ql/udf/ptf/TableFunctionResolver.java