fix test_metrics bug

fastNLP/core/metrics.py

@@ -9,7 +9,6 @@ To do:
 """
 import numpy as np
 import torch
-import sklearn.metrics as M
 import warnings
 
 def _conver_numpy(x):

test/test_metrics.py

@@ -1,7 +1,7 @@
 import sys, os
 sys.path = [os.path.join(os.path.dirname(__file__), '..')] + sys.path
 
-from fastNLP.action import metrics
+from fastNLP.core import metrics
 from sklearn import metrics as skmetrics
 import unittest
 import numpy as np