This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
public interface Function<I,O>
This is the core interface of the function api. The process is called
for every message of the input topic of the function. The incoming input bytes
are converted to the input type I for simple Java types(String, Integer, Boolean,
Map, and List types) and for org.Json type. If this serialization approach does not
meet your needs, you can use the byte stream handler defined in RawRequestHandler.