code: function findOne(coll, query, options, callback) {
    const cursor = coll
      .find(query, options)
      .limit(-1)
      .batchSize(1);
  
    // Return the item
    cursor.next((err, item) => {
      if (err != null) return handleCallback(callback, toError(err), null);
      handleCallback(callback, null, item);
    });
  }
docs: Fetch the first document that matches the query.
  
  @method
  @param {Collection} a Collection instance.
  @param {object} query Query for find Operation
  @param {object} [options] Optional settings. See Collection.prototype.findOne for a list of options.
  @param {Collection~resultCallback} [callback] The command result callback