How can i check if other mod is present?

So basically I want to register compatibility with TheOneProbe, something like that:

   private void onCommonSetup(final FMLCommonSetupEvent event) {
        ModNetworking.setup();
        ModGeneration.init();

		// if the one probe is installed
        TOPPlugin.registerCompatibility();
    }

I didn't test it without mod installed but i think it will fail when it's not present.

Thank you!