Importing function from Node.js module

Forgive me if I am doing something stupid, but I am just learning Node-Red and have a little knowledge of JavaScript.

I am trying to import the GTFS node from NPM into my Node-Red flow using a Function Node.

The example script provided uses the import syntax which doesn't appear to be available in Node-Red ( I have modified it to get the config value from the passed in message and output any errors using the node.error function.)

import { importGtfs } from 'gtfs';

const config = JSON.parse(msg.payload);

try {
  importGtfs(config);
} catch (error) {
  node.error(error);
}

I removed the import and tried to add the module in the function node's setup tab.
I can see that the module was downloaded and installed in the external modules folder, but I can't find a way to access the importGtfs function of the gtfs node module.
I have tried declaring the module as gtfs and accessing the function as gtfs.importGtfs, but this errors with TypeError: Cannot read properties of undefined (reading 'importGtfs')"
I tried a suggestion of using gtfs/importGtfs for the module name but this returns

Error: Cannot find module 'gtfs/importGtfs'
Require stack:
- /data/node_modules/gtfs/importGtfs

I have tried assigning the gtfs variable to the msg.payload to see what was returned but I just get undefined.

It would appear that the node is written using ES6, is this the cause of all my problems?

Any help would be appreciated.

Welcome to forums @dazfitzg.

You cant require or import in function nodes.

Please see a recent post on how to do it Here

EDIT:
Seems you have already tried that :man_facepalming:

I removed the import and tried to add the module in the function node's setup tab.