code: def receive_prepare(self, msg):
          '''
          Returns either a Promise or a Nack in response. The Acceptor's state must be persisted to disk
          prior to transmitting the Promise message.
          '''
          if self.promised_id is None or msg.proposal_id >= self.promised_id:
              self.promised_id = msg.proposal_id
              return Promise(self.network_uid, msg.from_uid, self.promised_id, self.accepted_id, self.accepted_value)
          else:
              return Nack(self.network_uid, msg.from_uid, msg.proposal_id, self.promised_idf receive_prepare(self, msg):
          '''
          Returns either a Promise or a Nack in response. The Acceptor's state must be persisted to disk
          prior to transmitting the Promise message.
          '''
          if self.promised_id is None or msg.proposal_id >= self.promised_id:
              self.promised_id = msg.proposal_id
              return Promise(self.network_uid, msg.from_uid, self.promised_id, self.accepted_id, self.accepted_value)
          else:
              return Nack(self.network_uid, msg.from_uid, msg.proposal_id, self.promised_id)
docs: Returns either a Promise or a Nack in response. The Acceptor's state must be persisted to disk
          prior to transmitting the Promise message.