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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 get_host_post_state(self):
 """Get the current state of system POST. Retrieves current state of system POST. :returns: POST state of the server. The valida states are:- null, Unknown, Reset, PowerOff, InPost, InPostDiscoveryComplete and FinishedPost. :raises: IloError, on an error from iLO """

        sushy_system = self._get_sushy_system(PROLIANT_SYSTEM_ID)
        return GET_POST_STATE_MAP.get(sushy_system.post_state)