in src/main/java/software/amazon/msk/auth/iam/internals/MSKCredentialProvider.java [257:262]
public List<AwsCredentialsProvider> getProviders() {
List<AwsCredentialsProvider> providers = new ArrayList<>();
getProfileProvider().ifPresent(providers::add);
getStsRoleProvider().ifPresent(providers::add);
return providers;
}