fix a little error in doc.

TODO: fix the bug doc of the class which inherit the class from outer space

fastNLP/core/metrics.py

@@ -152,6 +152,7 @@ class MetricBase(object):
     def get_metric_name(self):
         """
         返回metric的名称
+        
         :return:
         """
         return self._metric_name

fastNLP/core/optimizer.py

@@ -120,12 +120,11 @@ class AdamW(TorchOptimizer):
     The original Adam algorithm was proposed in `Adam: A Method for Stochastic Optimization`_.
     The AdamW variant was proposed in `Decoupled Weight Decay Regularization`_.
 
-    .. _Adam\: A Method for Stochastic Optimization:
-        https://arxiv.org/abs/1412.6980
-    .. _Decoupled Weight Decay Regularization:
-        https://arxiv.org/abs/1711.05101
-    .. _On the Convergence of Adam and Beyond:
-        https://openreview.net/forum?id=ryQu7f-RZ
+    .. _Adam\: A Method for Stochastic Optimization: https://arxiv.org/abs/1412.6980
+    
+    .. _Decoupled Weight Decay Regularization: https://arxiv.org/abs/1711.05101
+    
+    .. _On the Convergence of Adam and Beyond: https://openreview.net/forum?id=ryQu7f-RZ
     """
 
     def __init__(self, params, lr=1e-3, betas=(0.9, 0.999), eps=1e-8,