code: function insertDocsToDb(dburl, collectionName, docs, cb) {
    MongoClient.connect(dburl, function(err, db){
      if (err) {
        return cb(err);
      }
      var col = db.collection(collectionName);
      col.insertMany(docs, function(err, result){
        if (err) {
          return cb(err);
        }
        return cb(null, result);
      });
    });
  }
docs: Helper function to insert some documents to the given db and collection
  @param {String} dburl
  @param {String} collectionName
  @param {Array} docs
  @param {Function} cb