> db.getCollection('system.js').insert({     _id: "isTeenager",     value: function(age) {         return age >= 13 && age <= 19;     }, }) WriteResult({ "nInserted" : 1 }) > db.createCollection("ts", {timeseries: {timeField: "time"}}) { "ok" : 1 } > db.ts.insert({time: new Date(), name: 'Alice', age: 20}) WriteResult({ "nInserted" : 1 }) > db.runCommand({find: "ts", filter: {$where: "isTeenager(this.age)"}}) {         "ok" : 0,         "errmsg" : "$where is not allowed in this context",         "code" : 2,         "codeName" : "BadValue" } > db.foo.insert({name: 'Alice', age: 20}) WriteResult({ "nInserted" : 1 }) > db.runCommand({find: "foo", filter: {$where: "isTeenager(this.age)"}}) {         "cursor" : {                 "firstBatch" : [ ],                 "id" : NumberLong(0),                 "ns" : "test.foo"         },         "ok" : 1 }