def save_existing_iam_env_vars(self):
        """Backup IAM environment variables for later restoration."""
        for i in ['AWS_ACCESS_KEY_ID', 'AWS_SECRET_ACCESS_KEY',
                  'AWS_SESSION_TOKEN']:
            if i in self.env_vars:
                self.env_vars['OLD_' + i] = self.env_vars[i]
Backup IAM environment variables for later restoration.