python 错误：AxisError: axis -1 is out ……

pthon代码出现如下问题，不知道是何原因？谢谢！！！
runfile('D:/Python project/3Olive-lda2vec-master/examples/twenty_newsgroups/data/preprocess.py', wdir='D:/Python project/3Olive-lda2vec-master/examples/twenty_newsgroups/data')
Traceback (most recent call last):

File "", line 1, in
runfile('D:/Python project/3Olive-lda2vec-master/examples/twenty_newsgroups/data/preprocess.py', wdir='D:/Python project/3Olive-lda2vec-master/examples/twenty_newsgroups/data')

File "C:\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 710, in runfile
execfile(filename, namespace)

File "C:\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 101, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)

File "D:/Python project/3Olive-lda2vec-master/examples/twenty_newsgroups/data/preprocess.py", line 35, in
corpus.finalize()

File "D:\Python project\3Olive-lda2vec-master\lda2vec\corpus.py", line 155, in finalize
self.keys_loose, self.keys_counts, n_keys = self._loose_keys_ordered()

File "D:\Python project\3Olive-lda2vec-master\lda2vec\corpus.py", line 104, in _loose_keys_ordered
specials = np.sort(self.specials.values())

File "C:\Anaconda3\lib\site-packages\numpy\core\fromnumeric.py", line 822, in sort
a.sort(axis=axis, kind=kind, order=order)

AxisError: axis -1 is out of bounds for array of dimension 0