'Create a policy.
:type policy_name: string
:param policy_name: The name of the new policy
:type policy_document string
:param policy_document: The document of the new policy
:type path: string
:param path: The path in which the policy will be created.
Defaults to /.
:type description: string
:param path: A description of the new policy.'

def create_policy(self, policy_name, policy_document, path='/', description=None):

    params = {'PolicyName': policy_name, 'PolicyDocument': policy_document, 'Path': path}
    if (description is not None):
        params['Description'] = str(description)
    return self.get_response('CreatePolicy', params)
