Migration from 1.8 to 2.0, question about encoding in a shared class

More of a question than an issue.

Usage in multiple places is as follows:

A_Message message = ....
send(message)

or

B_Message message = ...
send(message)

Implementation of send() is as follows:
Question: How do I get encoded byte array from the message here? With 1.8, I could simply use message.toByteArray()

void send(Message<?,?> message)
    ::
    // doesn't work because message is not of type A_Message or B_Message
    ProtoAdapter.get(message).encode(message); 
    ::

The question centers on the shared send(Message message) method and the ProtoAdapter.get(message).encode(message) call, but names no repository files or tests. Start by locating those entry points and the 1.8-to-2.0 migration guidance; done would be documented, confirmed instructions for obtaining encoded bytes from the shared message type.