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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_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)