code: def _conn_from_arn(arn):
      
      arn = ARN(arn)
      if arn.error:
          raise CloudAuxException('Bad ARN: {arn}'.format(arn=arn))
      return dict(
          account_number=arn.account_number,
      )
docs: Extracts the account number from an ARN.
      :param arn: Amazon ARN containing account number.
      :return: dictionary with a single account_number key that can be merged with an existing
      connection dictionary containing fields such as assume_role, session_name, region.