docs: def init_config(policy_config):
      """Get policy lambda execution configuration.
  
      cli parameters are serialized into the policy lambda config,
      we merge those with any policy specific execution options.
  
      --assume role and -s output directory get special handling, as
      to disambiguate any cli context.
  
      account id is sourced from the config options or from api call
      and cached as a global
      """
      global account_id
  
      exec_options = policy_config.get('execution-options', {})
  
      # Remove some configuration options that don't make sense to translate from
      # cli to lambda automatically.
      #  - assume role on cli doesn't translate, it is the default lambda role and
      #    used to provision the lambda.
      #  - profile doesnt translate to lambda its `home` dir setup dependent
      #  - dryrun doesn't translate (and shouldn't be present)
      #  - region doesn't translate from cli (the lambda is bound to a region), and
      #    on the cli represents the region the lambda is provisioned in.
      for k in ('assume_role', 'profile', 'region', 'dryrun', 'cache'):
          exec_options.pop(k, None)
  
      # a cli local directory doesn't translate to lambda
      if not exec_options.get('output_dir', '').startswith('s3'):
          exec_options['output_dir'] = get_local_output_dir()
  
      # we can source account id from the cli parameters to avoid the sts call
      if exec_options.get('account_id'):
          account_id = exec_options['account_id']
  
      # merge with policy specific configuration
      exec_options.update(
          policy_config['policies'][0].get('mode', {}).get('execution-options', {}))
  
      # if using assume role in lambda ensure that the correct
      # execution account is captured in options.
      if 'assume_role' in exec_options:
          account_id = exec_options['assume_role'].split(':')[4]
      elif account_id is None:
          session = boto3.Session()
          account_id = get_account_id_from_sts(session)
      exec_options['account_id'] = account_id
  
      # Historical compatibility with manually set execution options
      # previously this was a boolean, its now a string value with the
      # boolean flag triggering a string value of 'aws'
      if 'metrics_enabled' in exec_options \
         and isinstance(exec_options['metrics_enabled'], bool) \
         and exec_options['metrics_enabled']:
          exec_options['metrics_enabled'] = 'aws'
  
      return Config.empty(**exec_options)