ImportError: cannot import name '_sample'

[yuanke]

ke.yuan@gpu04:/neural-ngram$ ll sample/
total 1084
drwxrwxr-x 4 ke.yuan ke.yuan 4096 Apr 14 02:32 ./
drwxrwxr-x 7 ke.yuan ke.yuan 4096 Apr 14 02:28 ../
drwxrwxr-x 5 ke.yuan ke.yuan 4096 Apr 14 02:39 build/
-rw-rw-r-- 1 ke.yuan ke.yuan 0 Apr 14 02:32 init.py
drwxrwxr-x 2 ke.yuan ke.yuan 4096 Apr 14 02:32 pycache/
-rw-rw-r-- 1 ke.yuan ke.yuan 908166 Apr 14 02:26 _sample.c
-rwxrwxr-x 1 ke.yuan ke.yuan 174312 Apr 14 02:26 _sample.cpython-36m-darwin.so*
-rw-rw-r-- 1 ke.yuan ke.yuan 1410 Apr 14 02:26 _sample.pyx
-rw-rw-r-- 1 ke.yuan ke.yuan 385 Apr 14 02:26 setup.py
ke.yuan@gpu04:/neural-ngram$'

ke.yuan@gpu04:~/neural-ngram$ python3 main.py train --name wiki --order 5 --batch-size 128
Traceback (most recent call last):
File "main.py", line 18, in
from softmax import ApproximateLoss
File "/home/ke.yuan/neural-ngram/softmax.py", line 12, in
from sample import _sample
ImportError: cannot import name '_sample'