def _generate_enums(hypothesis, reference, preprocess=str.lower):
    """
    Takes in string inputs for hypothesis and reference and returns
    enumerated word lists for each of them

    :param hypothesis: hypothesis string
    :type hypothesis: str
    :param reference: reference string
    :type reference: str
    :preprocess: preprocessing method (default str.lower)
    :type preprocess: method
    :return: enumerated words list
    :rtype: list of 2D tuples, list of 2D tuples
    """
    hypothesis_list = list(enumerate(preprocess(hypothesis).split()))
    reference_list = list(enumerate(preprocess(reference).split()))
    return hypothesis_list, reference_list