'Log GAN cost data. Called when minibatch is about to end
Arguments:
callback_data (HDF5 dataset): shared data between callbacks
model (Model): model object
epoch (int): index of current epoch
minibatch (int): index of minibatch that is ending'

def on_minibatch_end(self, callback_data, model, epoch, minibatch):

    if ((model.current_batch == model.last_gen_batch) and (model.last_gen_batch > 0)):
        mbstart = (callback_data['time_markers/minibatch'][(epoch - 1)] if (epoch > 0) else 0)
        callback_data['gan/gen_iter'][(mbstart + minibatch)] = model.gen_iter
        callback_data['gan/cost_dis'][(mbstart + minibatch)] = model.cost_dis[0]
