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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 update(self, volume_id, **kwargs):
 """ update an export """

        # These arguments are allowed
        self.allowed('update', kwargs,
                     ['status', 'instance_id',
                      'mountpoint', 'ip', 'initiator', 'session_ip',
                      'session_initiator'])
        # Remove parameters that are None
        params = self.unused(kwargs)
        return self.http_post('/volumes/%s/export' % volume_id, params=params)