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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def update_local_rt_nlris(self):
 """Does book-keeping of local RT NLRIs based on all configured VRFs. Syncs all import RTs and RT NLRIs. The method should be called when any VRFs are added/removed/changed. """

        current_conf_import_rts = set()
        for vrf in self._vrfs_conf.vrf_confs:
            current_conf_import_rts.update(vrf.import_rts)

        removed_rts = self._all_vrfs_import_rts_set - current_conf_import_rts
        new_rts = current_conf_import_rts - self._all_vrfs_import_rts_set
        self._all_vrfs_import_rts_set = current_conf_import_rts

        # Add new and withdraw removed local RtNlris
        for new_rt in new_rts:
            self.add_rt_nlri(new_rt)
        for removed_rt in removed_rts:
            self.add_rt_nlri(removed_rt, is_withdraw=True)