code: def stats(self, node_id=None, params=None):
          
          url = '/_cluster/stats'
          if node_id:
              url = _make_path('_cluster/stats/nodes', node_id)
          return self.transport.perform_request('GET', url, params=params)
docs: 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 timeout: Explicit operation timeout