text: # Copyright (C) 2015-2021 Regents of the University of California
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  """Caches all boto3 clients we instantiate."""
  import re
  
  from functools import lru_cache
  
  
  @lru_cache(maxsize=None)
  def client(*args, **kwargs):
      import boto3
      return boto3.client(*args, **kwargs)
  
  
  @lru_cache(maxsize=None)
  def resource(*args, **kwargs):
      import boto3
      return boto3.resource(*args, **kwargs)
  
  
  def zone_to_region(zone: str) -> str:
      """Get a region (e.g. us-west-2) from a zone (e.g. us-west-1c)."""
      # re.compile() caches the regex internally so we don't have to
      availability_zone = re.compile(r'^([a-z]{2}-[a-z]+-[1-9][0-9]*)([a-z])$')
      m = availability_zone.match(zone)
      if not m:
          raise ValueError(f"Can't extract region from availability zone '{zone}'")
      return m.group(1)
  