public static <T extends OperatorDesc> Operator<T> getAndMakeChild(
      T conf, RowSchema rwsch, Operator oplist0, Operator... oplist) {
    Operator<T> ret = getAndMakeChild(conf, oplist0, oplist);
    ret.setSchema(rwsch);
    return ret;
  }
Returns an operator given the conf and a list of parent operators.
ql/src/java/org/apache/hadoop/hive/ql/exec/OperatorFactory.java