presto-main/src/main/java/io/prestosql/sql/planner/SortExpressionExtractor.java/SortExpressionExtractor/BuildSymbolReferenceFinder
class SortExpressionExtractor:        public BuildSymbolReferenceFinder(Set<Symbol> buildSymbols)
        {
            this.buildSymbols = requireNonNull(buildSymbols, "buildSymbols is null").stream()
                    .map(Symbol::getName)
                    .collect(toImmutableSet());
        }