public void valid(String extensionName) {
        if (!inputExtensions.map().containsKey(extensionName))
            throw new IllegalArgumentException(String.format("Extension %s was not found in the original extensions", extensionName));
        validatedExtensions.put(extensionName, inputExtensions.map().get(extensionName));
    }
Validates a specific extension in the original {@code inputExtensions} map
@param extensionName - the name of the extension which was validated
clients/src/main/java/org/apache/kafka/common/security/oauthbearer/OAuthBearerExtensionsValidatorCallback.java