public static <T extends OperatorDesc> Operator<T> getAndMakeChild(CompilationOpContext cContext,
      T conf, RowSchema rwsch, List<Operator<? extends OperatorDesc>> oplist) {
    Operator<T> ret = getAndMakeChild(cContext, conf, 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