I training the frustum pointnet model and give me the following issue does anyone know how can i solve this problem:

I have added this :
ops = {‘pointclouds_pl’: pointclouds_pl,
‘one_hot_vec_pl’: one_hot_vec_pl,
‘labels_pl’: labels_pl,
‘centers_pl’: centers_pl,
‘heading_class_label_pl’: heading_class_label_pl,
‘heading_residual_label_pl’: heading_residual_label_pl,
‘size_class_label_pl’: size_class_label_pl,
‘size_residual_label_pl’: size_residual_label_pl,
‘is_training_pl’: is_training_pl,
‘logits’: end_points[‘mask_logits’],
‘centers_pred’: end_points[‘center’],
‘loss’: loss,
‘train_op’: train_op,
‘merged’: merged,
‘step’: batch,
‘end_points’: end_points}
in train def:
and added these two parts in train_epoch def
feed_dict = {ops[‘pointclouds_pl’]: batch_data,
ops[‘one_hot_vec_pl’]: batch_one_hot_vec,
ops[‘labels_pl’]: batch_label,
ops[‘centers_pl’]: batch_center,
ops[‘heading_class_label_pl’]: batch_hclass,
ops[‘heading_residual_label_pl’]: batch_hres,
ops[‘size_class_label_pl’]: batch_sclass,
ops[‘size_residual_label_pl’]: batch_sres,
ops[‘is_training_pl’]: is_training,}

    summary, step, _, loss_val, logits_val, centers_pred_val, \
    iou2ds, iou3ds = \
        sess.run([ops['merged'], ops['step'], ops['train_op'], ops['loss'],
            ops['logits'], ops['centers_pred'],
            ops['end_points']['iou2ds'], ops['end_points']['iou3ds']], 
            feed_dict=feed_dict) 

and give me this issues: merged is none
File “/home/aya/.local/lib/python3.8/site-packages/tensorflow/python/client/session.py”, line 265, in for_fetch
raise TypeError(f’Argument fetch = {fetch} has invalid type ’
TypeError: Argument fetch = None has invalid type “NoneType”. Cannot be None