<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def mount(self, app=None):
 """Mounts all registered routes to a bottle.py application instance. Args: app (instance):
 A `bottle.Bottle()` application instance. Returns: The Router instance (for chaining purposes). """

        for endpoint in self._routes:
            endpoint.register_app(app)

        return self