def start(self):
        """
        Start H2O cluster.
        The cluster is not up until wait_for_cloud_to_be_up() is called and returns.

        :return none
        """
        for node in self.nodes:
            node.start()

        for node in self.client_nodes:
            node.start()
Start H2O cluster.
        The cluster is not up until wait_for_cloud_to_be_up() is called and returns.

        :return none