presto-main/src/main/java/io/prestosql/util/SpatialJoinUtils.java/SpatialJoinUtils/getSymbolReferences
class SpatialJoinUtils:    private static Set<SymbolReference> getSymbolReferences(Collection<Symbol> symbols)
    {
        return symbols.stream().map(Symbol::toSymbolReference).collect(toImmutableSet());
    }