import node js modules inside Cypress typescript project

Question

I want to import a node module and add it to my command.ts in cypress. the tutorial suggests adding

import 'cypress-mailhog';

to the command.js file. when I add it to my command.ts file, I am not able to use the command for example

 cy.mhGetMailsBySubject

the error is TS2339: Property 'mhGetMailsBySubject' does not exist on type 'cy & EventEmitter'.

the modules I am trying to use is https://www.npmjs.com/package/cypress-mailhog

in my tsconfig.json file i have the following, among others

"target": "es6", 
"module": "commonjs", 
"lib": ["dom","es6", "es5", "dom.iterable"] 

How could I use mhGetMailsBySubject in my test case