map() not recognizing "text"
### Describe the bug

The [map() documentation](https://huggingface.co/docs/datasets/v2.14.5/en/package_reference/main_classes#datasets.Dataset.map) reads:
`
ds = ds.map(lambda x: tokenizer(x['text'], truncation=True, padding=True), batched=True)`

I have been trying to reproduce it in my code as:

`tokenizedDataset = dataset.map(lambda x: tokenizer(x['text']), batched=True)`

But it doesn't work as it throws the error:

> KeyError: 'text'

Can you please guide me on how to fix it?



### Steps to reproduce the bug

1. `from datasets import load_dataset

dataset = load_dataset("amazon_reviews_multi")`

2. Then this code: `from transformers import AutoTokenizer

tokenizer = AutoTokenizer.from_pretrained("bert-base-cased")`
3. The line I quoted above (which I have been trying)

### Expected behavior

As mentioned in the documentation, it should run without any error and map the tokenization on the whole dataset.

### Environment info

Python 3.10.2