def _conn_from_arn(arn):
arn = ARN(arn)<EOL>if arn.error:<EOL><INDENT>raise CloudAuxException('<STR_LIT>'.format(arn=arn))<EOL><DEDENT>return dict(<EOL>account_number=arn.account_number,<EOL>)<EOL>
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.