docs: def get_config_env_key(k: str) -> str:
      """
      Returns a scrubbed environment variable key, PULUMI_CONFIG_<k>, that can be used for
      setting explicit varaibles.  This is unlike PULUMI_CONFIG which is just a JSON-serialized bag.
      """
      env_key = ''
      for c in k:
          if c == '_' or 'A' <= c <= 'Z' or '0' <= c <= '9':
              env_key += c
          elif 'a' <= c <= 'z':
              env_key += c.upper()
          else:
              env_key += '_'
      return 'PULUMI_CONFIG_%s' % env_key