public SortOrder getSortOrder() {
      checkState(nullOrdering != UNDEFINED, "nullOrdering is undefined");
      if (ordering == ASCENDING) {
        if (nullOrdering == FIRST) {
          return ASC_NULLS_FIRST;
        }
        return ASC_NULLS_LAST;
      }
      checkState(ordering == DESCENDING);
      if (nullOrdering == FIRST) {
        return DESC_NULLS_FIRST;
      }
      return DESC_NULLS_LAST;
    }
Matches to any tree of nodes with children matching to given source matchers.
anyTree(tableScan("nation")) - will match to any plan which all leafs contain any node
containing table scan from nation table.

<p>Note: anyTree does not match zero nodes. E.g. output(anyTree(tableScan)) will NOT match
TableScan node followed by OutputNode.
iotdb-core/datanode/src/test/java/org/apache/iotdb/db/queryengine/plan/relational/planner/assertions/PlanMatchPattern.java