code: def key_pair(i, region, key_name):
      """
      If key_name is not None, key_pair will be named after key_name.
      Returns the ith default (aws_key_pair_name, key_pair_path).
      """
      if i == 0:
          key_pair_name = (
              "{}_{}".format(RAY, region)
              if key_name is None
              else key_name
          )
          return (
              key_pair_name,
              os.path.expanduser("~/.ssh/{}.pem".format(key_pair_name)),
          )
  
      key_pair_name = (
          "{}_{}_{}".format(RAY, i, region)
          if key_name is None
          else key_name + "_key-{}".format(i)
      )
      return (
          key_pair_name,
          os.path.expanduser("~/.ssh/{}.pem".format(key_pair_name)),
      )
  
imports: import copy
  import itertools
  import json
  import logging
  import os
  import time
  from collections import Counter
  from functools import lru_cache, partial
  from typing import Any, Dict, List, Optional, Set, Tuple
  import boto3
  import botocore
  from packaging.version import Version
  from ray.autoscaler._private.aws.cloudwatch.cloudwatch_helper import CloudwatchHelper
  from ray.autoscaler._private.aws.utils import LazyDefaultDict, handle_boto_error, resource_cache
  from ray.autoscaler._private.cli_logger import cf, cli_logger
  from ray.autoscaler._private.event_system import CreateClusterEvent, global_event_system
  from ray.autoscaler._private.providers import _PROVIDER_PRETTY_NAMES
  from ray.autoscaler._private.util import check_legacy_fields
  from ray.autoscaler.tags import NODE_TYPE_LEGACY_HEAD, NODE_TYPE_LEGACY_WORKER
label_desc: Use image node_id 1 for calling a global function with example usage: key_pair(i, region, key_name) and returns: key_pair_name,  os, key_pair_name,  os