<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def aws(self):
 """ Access the aws :returns: twilio.rest.accounts.v1.credential.aws.AwsList :rtype: twilio.rest.accounts.v1.credential.aws.AwsList """

        if self._aws is None:
            self._aws = AwsList(self._version, )
        return self._aws