Populates the DB from a sequence of strings, ERASING PREVIOUS STATE.

        :param seq: an iterable

def insert(self, seq):
        """
        Populates the DB from a sequence of strings, ERASING PREVIOUS STATE.

        :param seq: an iterable

        """
        # erase previous elements and make defaultdict for easier insertion.
        self._els_idxed = defaultdict(lambda: defaultdict(set))
        if type(seq) is str:
            raise ValueError('Provided argument should be a sequence of strings'
                             ', but not a string itself.')
        for el in seq:
            if type(el) is not str:
                raise ValueError('Element %s is not a string' % (el,))
            for gram in make_unique_ngrams(el, self.idx_size):
                self._els_idxed[gram][len(el)].add(el)

        # convert defaultdict to dict so as to not increase size when checking
        # for presence of an element
        self._finalize_db()