'Retrieve a list of all the identity versions which are supported by
this installation.
:rtype: ``list`` of :class:`.OpenStackIdentityVersion`'

def list_supported_versions(self):

    response = self.request('/', method='GET')
    result = self._to_versions(data=response.object['versions']['values'])
    result = sorted(result, key=(lambda x: x.version))
    return result
