'Converts a string to a vector (list of ints).
First runs a sentence tokenizer, then a word tokenizer.
``vec_type`` is the type of the returned vector if the input is a string.'

def txt2vec(self, text, vec_type=list):

    if (vec_type == np.ndarray):
        res = np.fromiter((self[token] for token in self.tokenize(str(text))), np.int)
    elif ((vec_type == list) or (vec_type == tuple) or (vec_type == set)):
        res = vec_type((self[token] for token in self.tokenize(str(text))))
    else:
        raise RuntimeError('Type    {}    not    supported    by    dict'.format(vec_type))
    assert (type(res) == vec_type)
    return res
