code: def assume_role_credentials(self, arn):
          
          log.info("Assuming role as %s", arn)
  
          # Clear out empty values
          for name in ['AWS_ACCESS_KEY_ID', 'AWS_SECRET_ACCESS_KEY', 'AWS_SECURITY_TOKEN', 'AWS_SESSION_TOKEN']:
              if name in os.environ and not os.environ[name]:
                  del os.environ[name]
  
          sts = self.amazon.session.client("sts")
          with self.catch_boto_400("Couldn't assume role", arn=arn):
              creds = sts.assume_role(RoleArn=arn, RoleSessionName="aws_syncr")
  
          return {
                'AWS_ACCESS_KEY_ID': creds["Credentials"]["AccessKeyId"]
              , 'AWS_SECRET_ACCESS_KEY': creds["Credentials"]["SecretAccessKey"]
              , 'AWS_SECURITY_TOKEN': creds["Credentials"]["SessionToken"]
              , 'AWS_SESSION_TOKEN': creds["Credentials"]["SessionToken"]
              }
docs: Return the environment variables for an assumed role