docs: public boolean isOrderDeterministic() {
          // Leaf nodes need to re-implement this test.
          assert(m_children != null);
          for (AbstractPlanNode child : m_children) {
              if (! child.isOrderDeterministic()) {
                  m_nondeterminismDetail = child.m_nondeterminismDetail;
                  return false;
              }
          }
          return true;
      }