[{_id:"bmasndvhjbcw",name:"lucas",occupation:"scientist",present_working:true,age:55,location:"texas"},{_id:"bmasndvhjbcx",name:"mark",occupation:"scientist",age:45,present_working:false,location:"texas"},{_id:"bmasndvhjbcq",name:"cooper",occupation:"physicist",age:69,location:"texas",present_working:false}]

db.collection.aggregate([{$project:{_id:1,name:1,occupation:1,age:1,location:1,present_working:{$cond:[{$eq:["$present_working",false]},"$$REMOVE","$present_working"]}}}])