presto-main/src/main/java/io/prestosql/sql/planner/optimizations/UnaliasSymbolReferences.java/UnaliasSymbolReferences/visitValues
class UnaliasSymbolReferences:        @Override
        public PlanNode visitValues(ValuesNode node, RewriteContext<Void> context)
        {
            List<List<Expression>> canonicalizedRows = node.getRows().stream()
                    .map(this::canonicalize)
                    .collect(toImmutableList());
            List<Symbol> canonicalizedOutputSymbols = canonicalizeAndDistinct(node.getOutputSymbols());
            checkState(node.getOutputSymbols().size() == canonicalizedOutputSymbols.size(), "Values output symbols were pruned");
            return new ValuesNode(
                    node.getId(),
                    canonicalizedOutputSymbols,
                    canonicalizedRows);
        }