'List policy versions.
:type policy_arn: string
:param policy_arn: The ARN of the policy to get versions of
:type marker: string
:param marker: A marker used for pagination (received from previous
accesses)
:type max_items: int
:param max_items: Send only max_items; allows paginations'

def list_policy_versions(self, policy_arn, marker=None, max_items=None):

    params = {'PolicyArn': policy_arn}
    if (marker is not None):
        params['Marker'] = marker
    if (max_items is not None):
        params['MaxItems'] = max_items
    return self.get_response('ListPolicyVersions', params, list_marker='Versions')
