code: @CheckReturnValue
      public GuildManager setAfkChannel(VoiceChannel afkChannel)
      {
          Checks.check(afkChannel == null || afkChannel.getGuild().equals(getGuild()), "Channel must be from the same guild");
          this.afkChannel = afkChannel == null ? null : afkChannel.getId();
          set |= AFK_CHANNEL;
          return this;
      }
docs: Sets the AFK {@link net.dv8tion.jda.core.entities.VoiceChannel VoiceChannel} of this {@link net.dv8tion.jda.core.entities.Guild Guild}.
  
  @param  afkChannel
  The new afk channel for this {@link net.dv8tion.jda.core.entities.Guild Guild}
  or {@code null} to reset
  
  @throws IllegalArgumentException
  If the provided channel is not from this guild
  
  @return GuildManager for chaining convenience