public RPCSendAdapter getSendAdapter(Version version) {
        Map.Entry<Version, RPCSendAdapter> lower = sendAdapters.floorEntry(version);
        return (lower != null) ? lower.getValue() : null;
    }
Determines and returns the send adapter that is compatible with the given version. If no adapter can be found,
this method returns null.

@param version the version for which to return an adapter
@return the compatible adapter
messagebus/src/main/java/com/yahoo/messagebus/network/rpc/RPCNetwork.java