code: function(V, is_training) {
        if(typeof(is_training) === 'undefined') is_training = false;
        var act = this.layers[0].forward(V, is_training);
        for(var i=1;i<this.layers.length;i++) {
          act = this.layers[i].forward(act, is_training);
        }
        return act;
      }
docs: forward prop the network. The trainer class passes is_training = true, but when this function is called from outside (not from the trainer), it defaults to prediction mode