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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_snapshot_attribute(self, snapshot_id, attribute='createVolumePermission'):
 """ Get information about an attribute of a snapshot. Only one attribute can be specified per call. :type snapshot_id: str :param snapshot_id: The ID of the snapshot. :type attribute: str :param attribute: The requested attribute. Valid values are: * createVolumePermission :rtype: list of :class:`boto.ec2.snapshotattribute.SnapshotAttribute` :return: The requested Snapshot attribute """

        params = {'Attribute' : attribute}
        if snapshot_id:
            params['SnapshotId'] = snapshot_id
        return self.get_object('DescribeSnapshotAttribute', params,
                               SnapshotAttribute, verb='POST')