<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def init_app(self, app, add_context_processor=True):
 """ Initialize with app configuration """


        # Check if login manager has been initialized
        if not hasattr(app, 'login_manager'):
            self.login_manager.init_app(
                app,
                add_context_processor=add_context_processor)

        # Clear flashed messages since we redirect to auth immediately
        self.login_manager.login_message = None
        self.login_manager.needs_refresh_message = None

        # Set default unauthorized callback
        self.login_manager.unauthorized_handler(self.unauthorized_callback)