public AWSCredentialsProvider getRequestCredentialsProvider() {
        return credentialsProvider;
    }
Returns the optional credentials provider to use to sign this request, overriding the default
credentials provider at the client level.

@return The optional credentials provider to use to sign this request, overriding the default
        credentials provider at the client level.
aws-java-sdk-core/src/main/java/com/amazonaws/AmazonWebServiceRequest.java