Add MetaShift dataset
I've started working on adding this dataset. I require some inputs on the following : 

Ref for the initial draft [here](https://github.com/dnaveenr/datasets/blob/add_metashift_dataset/datasets/metashift/metashift.py)
1. The dataset does not have a typical - train/test/val split. What do we do for the _split_generators() function ? How do we go about this ?
2. This dataset builds on the Visual Genome dataset, using a metadata file. The dataset is generated using generate_full_MetaShift.py script. By default, the authors choose to generate the dataset only for a SELECTED_CLASSES. The following script is used : 
Code : https://github.com/Weixin-Liang/MetaShift/blob/main/dataset/generate_full_MetaShift.py 
Info : https://metashift.readthedocs.io/en/latest/sub_pages/download_MetaShift.html#generate-the-full-metashift-dataset
Can I just copy over the required functions into the metashift.py to generate the dataset ?
3. How do we complete the _generate_examples for this dataset ?

The user has the ability to use default selected classes, get the complete dataset or add more specific additional classes. I think config would be a good option here.

Inputs, suggestions would be helpful. Thank you.
## Adding a Dataset
- **Name:** MetaShift
- **Description:**  collection of 12,868 sets of natural images across 410 classes-
- **Paper:** https://arxiv.org/abs/2202.06523v1
- **Data:** https://github.com/weixin-liang/metashift

Instructions to add a new dataset can be found [here](https://github.com/huggingface/datasets/blob/master/ADD_NEW_DATASET.md).

Add MetaShift dataset 
 ## Adding a Dataset
- **Name:** MetaShift
- **Description:**  collection of 12,868 sets of natural images across 410 classes-
- **Paper:** https://arxiv.org/abs/2202.06523v1
- **Data:** https://github.com/weixin-liang/metashift

Instructions to add a new dataset can be found [here](https://github.com/huggingface/datasets/blob/master/ADD_NEW_DATASET.md).
 
 I've started working on adding this dataset. I require some inputs on the following : 

Ref for the initial draft [here](https://github.com/dnaveenr/datasets/blob/add_metashift_dataset/datasets/metashift/metashift.py)
1. The dataset does not have a typical - train/test/val split. What do we do for the _split_generators() function ? How do we go about this ?
2. This dataset builds on the Visual Genome dataset, using a metadata file. The dataset is generated using generate_full_MetaShift.py script. By default, the authors choose to generate the dataset only for a SELECTED_CLASSES. The following script is used : 
Code : https://github.com/Weixin-Liang/MetaShift/blob/main/dataset/generate_full_MetaShift.py 
Info : https://metashift.readthedocs.io/en/latest/sub_pages/download_MetaShift.html#generate-the-full-metashift-dataset
Can I just copy over the required functions into the metashift.py to generate the dataset ?
3. How do we complete the _generate_examples for this dataset ?

The user has the ability to use default selected classes, get the complete dataset or add more specific additional classes. I think config would be a good option here.

Inputs, suggestions would be helpful. Thank you.