docs: def update_router(self, context, router_id, router):
          """Update an existing router in DB, and update it in Arista HW."""
  
          # Read existing router record from DB
          original_router = self.get_router(context, router_id)
          # Update router DB
          new_router = super(AristaL3ServicePlugin, self).update_router(
              context, router_id, router)
  
          # Modify router on the Arista Hw
          try:
              self.driver.update_router(context, router_id,
                                        original_router, new_router)
              return new_router
          except Exception:
              LOG.error(_LE("Error updating router on Arista HW router=%s "),
                        new_router)