text: var MongoClient = require('mongodb').MongoClient;
  
  MongoClient.connect('mongodb://localhost:27017/course', function (err, db) {
  
      if (err) throw err;
  
      var query = {
              'assignment': 'hw3'
          };
  
      db.collection('grades')
          .remove(query, function (err, removed) {
  
              if (err) throw err;
  
              console.dir('Successfully removed ' + removed + ' document');
  
              db.close();
          });
  
  });
  