'List available sizes.'

def list_sizes(self):

    sizes = []
    for value in INSTANCE_TYPES:
        key = value['id']
        size = CloudSigmaNodeSize(id=value['id'], name=value['name'], cpu=value['cpu'], ram=value['memory'], disk=value['disk'], bandwidth=value['bandwidth'], price=self._get_size_price(size_id=key), driver=self.connection.driver)
        sizes.append(size)
    return sizes
