How do you include a module/mixin in a presenter?

Question

I have a presenter in models/presenters/my_presenter.rb.

I have a mixin in lib/presenter_helper.rb.

I am trying to include the mixin inside my presenter. How do I include the mixin?

This is what I have right now, but it doesn't work:

class MyPresenter
  include PresenterHelper


end

I get the following error:

uninitialized constant MyPresenter::PresenterHelper (NameError)