def __setitem__(self, key, value):
        transformed = key.lower().translate(WordDictionary.number_transformation)
        super(WordDictionary, self).__setitem__(transformed, value)
Overrides the [] write operator. It converts every key to lower case
dataset/ETHPy150Open erickrf/nlpnet/nlpnet/word_dictionary.py/WordDictionary.__setitem__