Database
db={"teacher":[{"_id":ObjectId("64fee9b54273ac2234441225"),"teacherid":"64f1d72a4331bc8fc4c5930f","name":"Jackly"}],"users":[{_id:ObjectId("64f1d72a4331bc8fc4c5930f"),name:"Mark"}]}
Query
db.teacher.aggregate([{$match:{"teacherid":"64f1d72a4331bc8fc4c5930f"}},{$lookup:{from:"users",let:{teacherIdStr:"$teacherid"},pipeline:[{$match:{$expr:{$eq:["$_id",{$toObjectId:"$$teacherIdStr"}]}}}],as:"student"}},{$unset:"name"}])