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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 reference_handler(self, iobject, fact, attr_info, add_fact_kargs):
 """ Handler for facts that contain a reference to a fact. As shown below in the handler list, this handler is called when a attribute with key '@idref' on the fact's node is detected -- this attribute signifies that this fact does not contain a value but points to another object. Thus we either retrieve the object or, if an object with the given id does not yet exist, create a PLACEHOLDER object. We further create/refer to the fitting fact data type: we want the fact data type to express that the fact is a reference to an object. """


        logger.debug("XXX Found reference with %s" % attr_info)

        if 'idref' in attr_info:
            ref_key = 'idref'
            (namespace, namespace_uri, uid) = self.split_qname(attr_info[ref_key])
        elif fact['attribute'] and fact['attribute'] == 'phase_id':

            if fact['term']=='':
                return True
            else:
                (namespace, namespace_uri, uid) = self.split_qname(fact['value'])
        elif fact['attribute'] and fact['attribute'] == 'kill_chain_id':
            if fact['term'] == '':
                return True
            else:
                (namespace, namespace_uri, uid) = self.split_qname(fact['value'])

        timestamp = None

        if '@timestamp' in attr_info:
            timestamp = attr_info['@timestamp']

        #if not timestamp:
        #    timestamp = self.create_timestamp

        (target_mantis_obj, existed) = MantisImporter.create_iobject(
            uid=uid,
            identifier_ns_uri=namespace_uri,
            timestamp=timestamp,
            create_timestamp=self.default_timestamp)

        logger.debug("Creation of Placeholder for %s %s returned %s" % (namespace_uri, uid, existed))
        add_fact_kargs['value_iobject_id'] = Identifier.objects.get(uid=uid, namespace__uri=namespace_uri)

        return True