@Nullable
    default String serializeExampleRequest(
            String serviceName, String methodName, Object exampleRequest) {
        return null;
    }
Serializes the specified example request into a string.

@param serviceName the name of the service
@param methodName the name of the method
@param exampleRequest the example request

@return the serialized example, or {@code null} if not able to serialize.
core/src/main/java/com/linecorp/armeria/server/docs/DocServicePlugin.java