[UDF] n1ql query with advise returns Unexpected identifier

function advisequery() {

  var iter =  advise select airportname from `travel-sample` where city = 'Grenoble';

  let acc = [];

  for (const row of iter) {

    acc.push(row.advice.adviseinfo.recommended_indexes);

  }

  return {'num_entries': acc.length, 'data': acc};

} 

Error while compiling library. Cause:

compilation failed:

Exception: SyntaxError: Unexpected identifier

Location: functions/n1ql.js:1 

Code: function advisequery() {    var iter =  advise N1QL('select airportname from `travel-sample` where city \u003D \'Grenoble\';', {});    let acc = [];    for (const row of iter) {            acc.push(row.advice.adviseinfo.recommended_indexes);    }    return {'num_entries': acc.length, 'data': acc};} 

SyntaxError: Unexpected identifier 

    var iter =  N1QL("advise select airportname from `travel-sample` where city = 'Grenoble'", {});