'Create public ip.
:keyword instance_id: instance id for allocating public ip.
:type    instance_id: ``str``
:return public ip
:rtype ``str``'

def create_public_ip(self, instance_id):

    params = {'Action': 'AllocatePublicIpAddress', 'InstanceId': instance_id}
    resp = self.connection.request(self.path, params=params)
    return findtext(resp.object, 'IpAddress', namespace=self.namespace)
