private static ConcurrentMap<MessageType, Command> buildGfe81Commands() {
    final ConcurrentMap<MessageType, Command> commands = new ConcurrentHashMap<>();
    initializeGfe81Commands(commands);
    return commands;
  }
Iterate through all the Geode versions add a command to the map for that version

@return returns true if command was registered or same command was already registered,
        otherwise false.
@throws InternalGemFireError if a different command was already registered.
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/CommandInitializer.java