public static List<Operator<? extends OperatorDesc>> findSiblingOperators(
      Operator<? extends OperatorDesc> op)
      throws SemanticException {
    Operator<? extends OperatorDesc> child = getSingleChild(op, true);
    return child.getParentOperators();
  }
Find all sibling operators (which have the same child operator of op) of op (op
included).
@throws SemanticException
ql/src/java/org/apache/hadoop/hive/ql/optimizer/correlation/CorrelationUtilities.java