* Testing that encode_plus and batch_encode_plus behave the same way
Spoiler alert: they don't
* Testing rest of arguments in batch_encode_plus
* Test tensor return in batch_encode_plus
* Addressing Sam's comments
* flake8
* Simplified with `num_added_tokens`
* Preserve spaces in GPT-2 tokenizers
Preserves spaces after special tokens in GPT-2 and inhereted (RoBERTa)
tokenizers, enabling correct BPE encoding. Automatically inserts a space
in front of first token in encode function when adding special tokens.
* Add tokenization preprocessing method
* Add framework argument to pipeline factory
Also fixes pipeline test issue. Each test input now treated as a
distinct sequence.
