code: @CheckReturnValue
      public GuildAction addChannel(ChannelData channel)
      {
          Checks.notNull(channel, "Channel");
          this.channels.add(channel);
          return this;
      }
docs: Adds a {@link net.dv8tion.jda.core.entities.Channel Channel} to the resulting
  Guild. This cannot be of type {@link net.dv8tion.jda.core.entities.ChannelType#CATEGORY CATEGORY}!
  
  @param  channel
  The {@link net.dv8tion.jda.core.requests.restaction.GuildAction.ChannelData ChannelData}
  to use for the construction of the Channel
  
  @throws java.lang.IllegalArgumentException
  If the provided channel is {@code null}!
  
  @return The current GuildAction for chaining convenience