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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 check_ntp_status(self, ntp_status_int):
 """ check the NTP status """

        # convert the ntp_status integer value in a human readable value
        ntp_status_string = self.ntp_status.get(ntp_status_int, "unknown")

        if ntp_status_string == "unknown":
            return unknown, ("NTP status: " + ntp_status_string)

        # the ntp status should be synchronized (new MIB) or normalOperation (old mib)
        elif ntp_status_string != "synchronized" and ntp_status_string != "normalOperationPPS":
            # that is a critical condition, because the time reference will not be reliable anymore
            return critical, ("NTP status: " + ntp_status_string)

        return None