private static String getTrustPolicy() {
        return readResource(IAM_ROLE_TRUST_POLICY_DOCUMENT)
                .replace("{{CUSTOMER_ACCOUNT_ID}}", accountId);
    }
Method to return the trust policy document to create a role.

@return the trust policy document
src/samples/AmazonKinesisFirehose/AbstractAmazonKinesisFirehoseDelivery.java