'Create a policy version.
:type policy_arn: string
:param policy_arn: The ARN of the policy
:type policy_document string
:param policy_document: The document of the new policy version
:type set_as_default: bool
:param set_as_default: Sets the policy version as default
Defaults to None.'

def create_policy_version(self, policy_arn, policy_document, set_as_default=None):

    params = {'PolicyArn': policy_arn, 'PolicyDocument': policy_document}
    if (type(set_as_default) == bool):
        params['SetAsDefault'] = str(set_as_default).lower()
    return self.get_response('CreatePolicyVersion', params)
