Из-за чего возникает «too many values to unpack (expected 2)»?

quests = [line for line in open(path, encoding= 'UTF-8')]
replies = [line for line in open(path_, encoding= 'UTF-8')]


train_dataset = list(zip(quests, replies))

train_dataset = np.reshape(train_dataset, [-1, BATCH_SIZE, 2])

for (batch, (inp, tar)) in enumerate(train_dataset):
****

Traceback (most recent call last):
  File "evalite.py", line 488, in <module>
    for (batch, (inp, tar)) in enumerate(train_dataset):
ValueError: too many values to unpack (expected 2)