code: function geoHaystackSearch(coll, x, y, options, callback) {
    // Build command object
    let commandObject = {
      geoSearch: coll.s.name,
      near: [x, y]
    };
  
    // Remove read preference from hash if it exists
    commandObject = decorateCommand(commandObject, options, ['readPreference', 'session']);
  
    options = Object.assign({}, options);
    // Ensure we have the right read preference inheritance
    options.readPreference = resolveReadPreference(options, { db: coll.s.db, collection: coll });
  
    // Do we have a readConcern specified
    decorateWithReadConcern(commandObject, coll, options);
  
    // Execute the command
    executeCommand(coll.s.db, commandObject, options, (err, res) => {
      if (err) return handleCallback(callback, err);
      if (res.err || res.errmsg) handleCallback(callback, toError(res));
      // should we only be returning res.results here? Not sure if the user
      // should see the other return information
      handleCallback(callback, null, res);
    });
  }
docs: Execute a geo search using a geo haystack index on a collection.
  
  @method
  @param {Collection} a Collection instance.
  @param {number} x Point to search on the x axis, ensure the indexes are ordered in the same order.
  @param {number} y Point to search on the y axis, ensure the indexes are ordered in the same order.
  @param {object} [options] Optional settings. See Collection.prototype.geoHaystackSearch for a list of options.
  @param {Collection~resultCallback} [callback] The command result callback