def METHOD_NAME(self, node_id=None, params=None):
    """
    The Cluster Stats API allows to retrieve statistics from a cluster wide
    perspective. The API returns basic index metrics and information about
    the current nodes that form the cluster.
    `<http://www.elastic.co/guide/en/elasticsearch/reference/current/cluster-stats.html>`_
    :arg node_id: A comma-separated list of node IDs or names to limit the
        returned information; use `_local` to return information from the
        node you're connecting to, leave empty to get information from all
        nodes
    :arg flat_settings: Return settings in flat format (default: false)
    :arg human: Whether to return time and byte values in human-readable
        format., default False
    """
    url = '/_cluster/stats'
    if node_id:
        url = _make_path('_cluster/stats/nodes', node_id)
    _, data = self.transport.perform_request('GET', url, params=params)
    return data