<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_urls(self):
 """ Generate the list of URL patterns including the registered single object routers urls. """

        base_urls = super(SimpleRouter, self).get_urls()
        single_urls = sum([r.urls for r in self._single_object_registry], [])
        nested_urls = sum([r.urls for r in self._nested_object_registry], [])

        return base_urls + single_urls + nested_urls