TypeError: 'NoneType' object is not callable
> * For the platform, we need to know the operating system of your machine. Could you please run the command `datasets-cli env` and copy-and-paste its output below?
> * In relation with the error, you just gave us the error type and message (`TypeError: 'NoneType' object is not callable`). Could you please copy-paste the complete stack trace, so that we know exactly which part of the code threw the error?

1. For the platform, here are the output:
        - datasets` version: 1.11.0
        - Platform: Windows-10-10.0.19041-SP0
        - Python version: 3.7.10
        - PyArrow version: 5.0.0
2. For the code and error：
     ```python
     from datasets import load_dataset, load_metric
     dataset = load_dataset("glue", "cola")
    ```
    ```python
    Traceback (most recent call last):
    ....
    ....
    File "my_file.py", line 2, in <module>
    dataset = load_dataset("glue", "cola")
    File "My environments\lib\site-packages\datasets\load.py", line 830, in load_dataset
    **config_kwargs,
     File "My environments\lib\site-packages\datasets\load.py", line 710, in load_dataset_builder
    **config_kwargs,
    TypeError: 'NoneType' object is not callable
    ```
   Thank you!
## Describe the bug

TypeError: 'NoneType' object is not callable
## Steps to reproduce the bug
```python
from datasets import load_dataset, load_metric
dataset = datasets.load_dataset("glue", 'cola')
```

## Expected results
A clear and concise description of the expected results.

## Actual results
Specify the actual results or traceback.

## Environment info
<!-- You can run the command `datasets-cli env` and copy-and-paste its output below. -->
- `datasets` version: 1.11.0
- Platform:
- Python version: 3.7
- PyArrow version:

TypeError: 'NoneType' object is not callable 
 ## Describe the bug

TypeError: 'NoneType' object is not callable
## Steps to reproduce the bug
```python
from datasets import load_dataset, load_metric
dataset = datasets.load_dataset("glue", 'cola')
```

## Expected results
A clear and concise description of the expected results.

## Actual results
Specify the actual results or traceback.

## Environment info
<!-- You can run the command `datasets-cli env` and copy-and-paste its output below. -->
- `datasets` version: 1.11.0
- Platform:
- Python version: 3.7
- PyArrow version:
 
 > * For the platform, we need to know the operating system of your machine. Could you please run the command `datasets-cli env` and copy-and-paste its output below?
> * In relation with the error, you just gave us the error type and message (`TypeError: 'NoneType' object is not callable`). Could you please copy-paste the complete stack trace, so that we know exactly which part of the code threw the error?

1. For the platform, here are the output:
        - datasets` version: 1.11.0
        - Platform: Windows-10-10.0.19041-SP0
        - Python version: 3.7.10
        - PyArrow version: 5.0.0
2. For the code and error：
     ```python
     from datasets import load_dataset, load_metric
     dataset = load_dataset("glue", "cola")
    ```
    ```python
    Traceback (most recent call last):
    ....
    ....
    File "my_file.py", line 2, in <module>
    dataset = load_dataset("glue", "cola")
    File "My environments\lib\site-packages\datasets\load.py", line 830, in load_dataset
    **config_kwargs,
     File "My environments\lib\site-packages\datasets\load.py", line 710, in load_dataset_builder
    **config_kwargs,
    TypeError: 'NoneType' object is not callable
    ```
   Thank you!