in src/main/java/software/amazon/msk/auth/iam/internals/MSKCredentialProvider.java [229:234]
StsClient getStsClientForDebuggingCreds(AwsCredentials credentials) {
return StsClient.builder()
.credentialsProvider(StaticCredentialsProvider.create(credentials))
.region(Region.of(stsRegion))
.build();
}