import io.cloudevents.CloudEvent;
import io.cloudevents.core.format.EventFormatProvider;
import io.cloudevents.core.builder.CloudEventBuilder;
import io.cloudevents.core.format.ContentType; // New constant to facilitate loose coupling in client applications

CloudEvent event = ...;

byte[] serialized = EventFormatProvider
    .getInstance()
    .resolveFormat(ContentType.PROTO) // EventFormatProvider.resolveFormat(...) overloaded 
    .serialize(event);                // for string and enum input options