Creating a RelNode list from a logical Plan

[Γιώργος Θεοδωράκης]

Hello,
I have a logical plan as RelNode, and I want to break it into single
operators and get a list of RelNodes. With RelNode.getInputs() I get every
node except the parent. How do I get the parent node? For example, I have

LogicalProject(orderid=[$0], productid=[$1], units=[$2])
  LogicalFilter(condition=[AND(>($2, 5), >(1, 4), =(3, 4))])
    LogicalTableScan(table=[[s, orders]])

and I can't get the LogicalProject Node.

Thanks,
George