AT dispatchPacket

Hey I want to make dispatchPacket method in NetworkManager public. Problem is I cant figure out the correct JVM name for io.netty.util.concurrent.GenericFutureListener; I tried it like this:

public net.minecraft.network.NetworkManager func_150732_b(Lnet/minecraft/network/Packet;Lio/netty/util/concurrent/GenericFutureListener;)V

but it says 1 Broken Access Transformer lines:
— net.minecraft.network.NetworkManager func_150732_b(Lnet/minecraft/network/Packet;Lio/netty/util/concurrent/GenericFutureListener;)V