docstr: Returns the head node's id and the list of all worker node ids,
  given a list `nodes` of all node ids in the cluster.
docstr_tok: ["Returns","the","head","node","'s","id","and","the","list","of","all","worker","node","ids",",","given","a","list","`","nodes","`","of","all","node","ids","in","the","cluster","."]
code: def _get_head_and_workers(
      self, nodes: List[NodeID]
  ) -> Tuple[NodeID, List[NodeID]]:
      """Returns the head node's id and the list of all worker node ids,
      given a list `nodes` of all node ids in the cluster.
      """
      head_id, worker_ids = None, []
      for node in nodes:
          tags = self.provider.node_tags(node)
          if tags[TAG_RAY_NODE_KIND] == NODE_KIND_HEAD:
              head_id = node
          elif tags[TAG_RAY_NODE_KIND] == NODE_KIND_WORKER:
              worker_ids.append(node)
      return head_id, worker_ids
  
imports: import collections
  import copy
  import logging
  import os
  from abc import abstractmethod
  from functools import partial
  from typing import Callable, Dict, List, Optional, Tuple
  import ray
  from ray._private.gcs_utils import PlacementGroupTableData
  from ray.autoscaler._private.constants import AUTOSCALER_CONSERVE_GPU_NODES, AUTOSCALER_UTILIZATION_SCORER_KEY
  from ray.autoscaler._private.loader import load_function_or_class
  from ray.autoscaler._private.node_provider_availability_tracker import NodeAvailabilitySummary
  from ray.autoscaler._private.util import NodeID, NodeIP, NodeType, NodeTypeConfigDict, ResourceDict, is_placement_group_resource
  from ray.autoscaler.node_provider import NodeProvider
  from ray.autoscaler.tags import NODE_KIND_HEAD, NODE_KIND_UNMANAGED, NODE_KIND_WORKER, TAG_RAY_NODE_KIND, TAG_RAY_USER_NODE_TYPE
  from ray.core.generated.common_pb2 import PlacementStrategy
label_desc: Use image node_id 2 for calling the ResourceDemandScheduler obj's underlying member method code with example usage: obj._get_head_and_workers(nodes) and returns: head_id,  worker_ids