concatenate_datasets support axis=0 or 1 ？
Unfortunately `concatenate_datasets` only supports concatenating the rows, while what you want to achieve is concatenate the columns.
Currently to add more columns to a dataset, one must use `map`.
What you can do is somehting like this:
```python
# suppose you have datasets d1, d2, d3
def add_columns(example, index):
    example.update(d2[index])
    example.update(d3[index])
    return example

full_dataset = d1.map(add_columns, with_indices=True)
```
I want to achieve the following result
![image](https://user-images.githubusercontent.com/12437751/99207426-f0c8db80-27f8-11eb-820a-4d9f7287b742.png)

concatenate_datasets support axis=0 or 1 ？ 
 I want to achieve the following result
![image](https://user-images.githubusercontent.com/12437751/99207426-f0c8db80-27f8-11eb-820a-4d9f7287b742.png)
 
 Unfortunately `concatenate_datasets` only supports concatenating the rows, while what you want to achieve is concatenate the columns.
Currently to add more columns to a dataset, one must use `map`.
What you can do is somehting like this:
```python
# suppose you have datasets d1, d2, d3
def add_columns(example, index):
    example.update(d2[index])
    example.update(d3[index])
    return example

full_dataset = d1.map(add_columns, with_indices=True)
```