AttributeError: module 'pyarrow' has no attribute 'PyExtensionType' during import 
Installing datasets installs pyarrow>=0.17.1 so in theory it doesn't matter which version of pyarrow colab has by default (which is currently pyarrow 0.14.1).

Also now the colab runtime refresh the pyarrow version automatically after the update from pip (previously you needed to restart your runtime).

I guess what happened is that Colab didn't refresh pyarrow for some reason, and the AttributeError was raised *before* the pyarrow version check from `datasets` at https://github.com/huggingface/datasets/blob/master/src/datasets/__init__.py#L60
I'm using Colab. And suddenly this morning, there is this error. Have a look below!

![screenshot-colab research google com-2021 01 26-08-15-36](https://user-images.githubusercontent.com/45964869/105799890-fdaf3b80-5fae-11eb-8f06-11b65cdccc30.png)

AttributeError: module 'pyarrow' has no attribute 'PyExtensionType' during import  
 I'm using Colab. And suddenly this morning, there is this error. Have a look below!

![screenshot-colab research google com-2021 01 26-08-15-36](https://user-images.githubusercontent.com/45964869/105799890-fdaf3b80-5fae-11eb-8f06-11b65cdccc30.png)
 
 Installing datasets installs pyarrow>=0.17.1 so in theory it doesn't matter which version of pyarrow colab has by default (which is currently pyarrow 0.14.1).

Also now the colab runtime refresh the pyarrow version automatically after the update from pip (previously you needed to restart your runtime).

I guess what happened is that Colab didn't refresh pyarrow for some reason, and the AttributeError was raised *before* the pyarrow version check from `datasets` at https://github.com/huggingface/datasets/blob/master/src/datasets/__init__.py#L60