@FunctionalInterface
public interface Rpc<I extends RpcInput, O extends RpcOutput> {
    /**
     * Invoke the Rpc.
     *
     * @param input Input argument
     * @return Future result of invocation
     * @throws NullPointerException if any of the arguments are null
     */
    @CheckReturnValue
    @NonNull ListenableFuture<@NonNull RpcResult<@NonNull O>> invoke(@NonNull I input);
} 

@FunctionalInterface
public interface Foo extends Rpc<FooInput, FooOutput> {
    // perhaps private with qname() method?
   public static final @NonNull QName QNAME = $YangModuleInfoImpl.qnameOf("foo-act");
}