I am trying to set up my app to use the same sort of modules and routing as in the example here:

https://angular.io/guide/router#the-sample-application

It works fine, but when I try to use a MDB element in my submodule, I get an error similiar to this:

If 'mdb-side-nav' is an Angular component and it has 'sidenavBreakpoint' input, then verify that it is part of this module.

It works fine if I put MDBBootstrapModulesPro.forRoot() in each sub module, but is there a way to put it in the app.module.ts so it is available in all sub modules.