'Count (UI, OI) when stemming is done by truncating words at \'cutlength\'.
:param words: Words used for the analysis
:param cutlength: Words are stemmed by cutting them at this length
:type words: set(str) or list(str)
:type cutlength: int
:return: Understemming and overstemming indexes
:rtype: tuple(int, int)'

def _get_truncation_indexes(self, words, cutlength):

    truncated = _truncate(words, cutlength)
    (gumt, gdmt, gwmt, gdnt) = _calculate(self.lemmas, truncated)
    (ui, oi) = _indexes(gumt, gdmt, gwmt, gdnt)[:2]
    return (ui, oi)
