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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 notify_engine_activated(self, chain_head):
 """The consensus engine has been activated."""

        chain_head_bytes = chain_head.SerializeToString()
        self._notify(
            "consensus_notifier_notify_engine_activated",
            chain_head_bytes,
            len(chain_head_bytes))