Unable to use custom dataset: AttributeError: 'list' object has no attribute 'keys'
What am I doing wrong?

I encode data with
```
model_name = "dbmdz/bert-base-italian-uncased"
tokenizer = AutoTokenizer.from_pretrained(model_name, do_lower_case = True)

def encode_data(texts):
    return tokenizer.batch_encode_plus(
                texts, 
                add_special_tokens=True, 
                return_attention_mask=True, 
                padding = True,
                truncation=True,
                max_length=200,
                return_tensors='pt'
            )
```
Then I create my datasets with
```
import torch

class my_Dataset(torch.utils.data.Dataset):
    def __init__(self, encodings, labels):
        self.encodings = encodings
        self.labels = torch.tensor(labels)

    def __getitem__(self, idx):
        item = {key: val[idx] for key, val in self.encodings.items()}
        item['labels'] = self.labels[idx]
        print(item)
        return item

    def __len__(self):
        return len(self.labels)
```
So I have
```
encoded_data_train = encode_data(df_train['text'].tolist())
encoded_data_val = encode_data(df_val['text'].tolist())
encoded_data_test = encode_data(df_test['text'].tolist())
dataset_train = my_Dataset(encoded_data_train, df_train['labels'].tolist())
dataset_val = my_Dataset(encoded_data_val, df_val['labels'].tolist())
dataset_test = my_Dataset(encoded_data_test, df_test['labels'].tolist())
```
Then I initiate my Trainer with
```
from transformers import AutoConfig, TrainingArguments, DataCollatorWithPadding, Trainer

training_args = TrainingArguments(
    output_dir='/trial',
    learning_rate=1e-6,
    do_train=True,
    do_eval=True,
    evaluation_strategy='epoch',
    num_train_epochs=10,
    per_device_train_batch_size=8,
    per_device_eval_batch_size=8,
    warmup_steps=0,
    weight_decay=0.2,
    logging_dir="./logs",
)

num_labels = len(label_dict)
model = AutoModelForSequenceClassification.from_pretrained(model_name,num_labels = num_labels)

trainer = Trainer(
  model=model,
  args=training_args,
  data_collator=DataCollatorWithPadding(tokenizer),
  tokenizer= tokenizer,
  train_dataset=dataset_train,
  eval_dataset=dataset_val,
)
```
and finally I train
```
trainer.train()
```
Here is the error I get
```
AttributeErrorTraceback (most recent call last)
<ipython-input-22-5d018b4b061d> in <module>
----> 1 trainer.train()

/opt/conda/lib/python3.8/site-packages/transformers/trainer.py in train(self, resume_from_checkpoint, trial, **kwargs)
   1032             self.control = self.callback_handler.on_epoch_begin(self.args, self.state, self.control)
   1033 
-> 1034             for step, inputs in enumerate(epoch_iterator):
   1035 
   1036                 # Skip past any already trained steps if resuming training

/opt/conda/lib/python3.8/site-packages/torch/utils/data/dataloader.py in __next__(self)
    433         if self._sampler_iter is None:
    434             self._reset()
--> 435         data = self._next_data()
    436         self._num_yielded += 1
    437         if self._dataset_kind == _DatasetKind.Iterable and \

/opt/conda/lib/python3.8/site-packages/torch/utils/data/dataloader.py in _next_data(self)
    473     def _next_data(self):
    474         index = self._next_index()  # may raise StopIteration
--> 475         data = self._dataset_fetcher.fetch(index)  # may raise StopIteration
    476         if self._pin_memory:
    477             data = _utils.pin_memory.pin_memory(data)

/opt/conda/lib/python3.8/site-packages/torch/utils/data/_utils/fetch.py in fetch(self, possibly_batched_index)
     45         else:
     46             data = self.dataset[possibly_batched_index]
---> 47         return self.collate_fn(data)

/opt/conda/lib/python3.8/site-packages/transformers/data/data_collator.py in __call__(self, features)
    116 
    117     def __call__(self, features: List[Dict[str, Union[List[int], torch.Tensor]]]) -> Dict[str, torch.Tensor]:
--> 118         batch = self.tokenizer.pad(
    119             features,
    120             padding=self.padding,

/opt/conda/lib/python3.8/site-packages/transformers/tokenization_utils_base.py in pad(self, encoded_inputs, padding, max_length, pad_to_multiple_of, return_attention_mask, return_tensors, verbose)
   2558         if self.model_input_names[0] not in encoded_inputs:
   2559             raise ValueError(
-> 2560                 "You should supply an encoding or a list of encodings to this method"
   2561                 f"that includes {self.model_input_names[0]}, but you provided {list(encoded_inputs.keys())}"
   2562             )

AttributeError: 'list' object has no attribute 'keys'
```
What I am doing wrong?
I also tried using
```
import torch
from torch.utils.data import TensorDataset

dataset_train = TensorDataset(encoded_data_train['input_ids'], encoded_data_train['attention_mask'], torch.tensor(df_train['labels'].tolist()))
dataset_test = TensorDataset(encoded_data_test['input_ids'], encoded_data_test['attention_mask'], torch.tensor(df_test['labels'].tolist()))
dataset_val = TensorDataset(encoded_data_val['input_ids'], encoded_data_val['attention_mask'], torch.tensor(df_val['labels'].tolist()))
```
getting the same error.
Using:
torch == 1.7.1
transformers == 4.4.2

Thank you!

@sgugger 
This is really weird. Could you print a few items of your Dataset? The error means that they are not dictionaries containing `"input_ids"` but they certainly seem to be.

Also note that since you already have applied padding in your preprocessing, you can use the `default_data_collator`, but the code should work nonetheless.<|||||>> Also note that since you already have applied padding in your preprocessing, you can use the `default_data_collator`, but the code should work nonetheless.

Yeah, I did try commenting the line about the data_collator as well, but I got the same error.

> This is really weird. Could you print a few items of your Dataset? The error means that they are not dictionaries containing `"input_ids"` but they certainly seem to be.

For instance, `dataset_train.__getitem__(1)` gives me
```
{'input_ids': tensor([  102,  2719, 10118, 19614,   784,   366,   119,   142, 17586,   113,
         10885,  4019,  5129,   143, 10885,   119,  4019, 14633,  1354,   137,
           917,  1621,  9048,   360,   151,   143,   784,   366,   113,   213,
          7809,   985,  1941,  1702,  9580,   749, 12993,   135,  9272,   119,
          1202,  1328,  2909,  7427,  2909,   483, 15079,  6766,  2201,  5754,
          4213,  1266,   642,   119,  1968,   115,  7584,  7124,  2899,  9654,
           151,   143,  3684,   137, 17586,   113,  3151,   113,   193,  4283,
           165,  1035,  1354,  4913,  1621,  9048,   360,   137, 17586,   113,
           119,  7809,   985,  1941,  1702,  1621,  9048,   360,  4913, 16829,
           913,   272,  3694,  2909,  7427,   145,  1723, 20957, 15016,   213,
         11171,   119,  7809,   642,  3761,   188,   164,  4706,   119,  3684,
          8941,   119,  6330,  8076,  2199,   642, 23829, 22462, 30934,  4213,
          1354,  2759,   311,  7809,  5434,   137,  1031,   510,  2603,  5569,
          5434,   137,  1031,   510,  3732,  5569,  5434,   137,  1031,   510,
          3627, 14715, 30951,  4543,  8823,  5066,  3625,  3627,  1701,  7900,
           153,  5066,  3625,  3732,  7559,   127,  3732, 13703,   133,   176,
         11576,  2909, 13703,   133,  1621,  9048,   360,  1723,  5230,  9580,
           749, 12993,   114,  1031,   510,   387, 11993,   189, 22264,  8823,
           143,  6766,  3462,  5622, 27082,   113,  7809,  3132,  1011,   189,
          7825,  8823,   143,  6766,   111,   341,  7124,  2899, 18482,   103]),
 'token_type_ids': tensor([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
         0, 0, 0, 0, 0, 0, 0, 0]),
 'attention_mask': tensor([1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
         1, 1, 1, 1, 1, 1, 1, 1]),
 'labels': tensor(5)}
```
Input texts are emails in italian.

(the issue appears also with transformers 4.5.1)<|||||>I am unable to reproduce your bug. Are you sure your data frames don't contain a list of text in one of the line instead of just texts?<|||||>I found the mistake! I was doing something slightly different from what I wrote, namely
``` 
from transformers import AutoConfig, TrainingArguments, DataCollatorWithPadding, Trainer

train_dataset=dataset_train,
eval_dataset = dataset_val

training_args = TrainingArguments(
    output_dir='/trial',
    learning_rate=1e-6,
    do_train=True,
    do_eval=True,
    evaluation_strategy='epoch',
    num_train_epochs=10,
    per_device_train_batch_size=8,
    per_device_eval_batch_size=8,
    warmup_steps=0,
    weight_decay=0.2,
    logging_dir="./logs",
)

num_labels = len(label_dict)
model = AutoModelForSequenceClassification.from_pretrained(model_name,num_labels = num_labels)

trainer = Trainer(
  model=model,
  args=training_args,
  data_collator=DataCollatorWithPadding(tokenizer),
  tokenizer= tokenizer,
  train_dataset=train_dataset,
  eval_dataset=eval_dataset,
)
```
The difference is in line 3 and 4, and consequently last two lines. The mistake is the comma at the end of line 3. My bad I did not run the example code I published in the question exactly as it was. I am so sorry, and so upset to have spent a week for a stupid comma.
Thanks for the help<|||||>Oh that's a nasty little bug indeed! Glad you found the problem!