minor fix (#2961)

ppdet/data/source/coco_loader.py

@@ -13,9 +13,6 @@
 # limitations under the License.
 
 import numpy as np
-import matplotlib
-matplotlib.use('Agg')
-
 from pycocotools.coco import COCO
 
 import logging

ppdet/utils/coco_eval.py

@@ -22,6 +22,8 @@ import sys
 import json
 import cv2
 import numpy as np
+import matplotlib
+matplotlib.use('Agg')
 from pycocotools.coco import COCO
 from pycocotools.cocoeval import COCOeval
 import pycocotools.mask as mask_util

ppdet/utils/stats.py

@@ -61,8 +61,5 @@ class TrainingStats(object):
 
     def log(self, extras=None):
         d = self.get(extras)
-        strs = ', '.join(
-            str(dict({
-                x.encode('utf-8'): y
-            })).strip('{}') for x, y in d.items())
+        strs = ', '.join(str(dict({x: y})).strip('{}') for x, y in d.items())
         return strs