presto-parser/src/main/java/io/prestosql/sql/parser/AstBuilder.java/AstBuilder/visitShowFunctions
class AstBuilder:    @Override
    public Node visitShowFunctions(SqlBaseParser.ShowFunctionsContext context)
    {
        return new ShowFunctions(getLocation(context),
                getTextIfPresent(context.pattern)
                        .map(AstBuilder::unquote),
                getTextIfPresent(context.escape)
                        .map(AstBuilder::unquote));
    }