What is the default datatype for the emotions dataset (one of huggingface's site dataset)?

Question

I'm working with the emotions dataset from HuggingFace library.

I know I can switch its presentation format to pandas by doing:

emotions.set_format(type='pandas')

And I can switch it back to its default presentation format by doing:

emotions.reset_format()

My doubts are two: 1st) what types are allowed besides 'pandas'? and 2nd) what is the name of the default format? I tried looking on internet and on some books but found nothing.