protected LOJsonAdaptor convertNodeToAdaptor(LogicalRelationalOperator node, LogicalPlan lp)
throws FrontendException {
if (node instanceof LOLoad) {
return new LOLoadJsonAdaptor((LOLoad) node, lp);
} else if (node instanceof LOStore) {
return new LOStoreJsonAdaptor((LOStore) node, lp);
} else if (node instanceof LOSplitOutput) {
return new LOSplitOutputJsonAdaptor((LOSplitOutput) node, lp);
} else if (node instanceof LOJoin) {
return new LOJoinJsonAdaptor((LOJoin) node, lp);
} else if (node instanceof LOCogroup) {