Function train_epoch

(train_loader, val_loader, model, criterion, optimizer, epoch,
                train_writer, val_writer,
                train_loss_meter, val_loss_meter,
                depth_loss_meter, grad_loss_meter,
                normals_loss_meter,
                date_str, model_save_path,
                args,
                boundary_loss_meter=None, consensus_loss_meter=None)