commenting source of tokenizer

class SmilesTokenizer(BertTokenizer):

    r"""

    Constructs a SmilesTokenizer.

    Mostly copied from https://github.com/huggingface/transformers

    Bulk of code is from https://github.com/huggingface/transformers and https://github.com/rxn4chemistry/rxnfp

    Args:

        vocab_file: Path to a SMILES character per line vocabulary file

    """