presto-parser/src/main/java/io/prestosql/sql/parser/AstBuilder.java/AstBuilder/getGrantorSpecificationIfPresent
class AstBuilder:    private Optional<GrantorSpecification> getGrantorSpecificationIfPresent(SqlBaseParser.GrantorContext context)
    {
        return Optional.ofNullable(context).map(this::getGrantorSpecification);
    }