Is it possible to access af function defined on the website with Testcafé?

Lets say 'mywebsite.com' has a global function:

function sayHello(message){
console.log(message)
}

is it possible to run a test of that function with testcafé in nodejs?

So far i have this

import { Selector } from 'testcafe';

fixture `mywebsite test`
    .page `http://mywebsite.com`;

test('sayHelloFuncTest', async t => {

    sayHello('HELLO!')

});

This will give me an error saying: ReferenceError: sayHello is not defined

So is there a way to access the sayHello() function?