Custom integration communication with Home assistant

so i posted a pull request for a custom integration and got the following feedback:
" 1. Not reference home assistant, everything that should happen to Home Assistant (like registering HTTP views) should happen in the integration code"

basically i’m passing the hass object to my library to do two things:
1- register some http reviews
2- listen to specific events fired by entities

i understand that i need to remove the registeration part to the integration code, but what about the events part?
is there a specific way that an integration should communicate with Home assistant?
thanks